# Fields

> Insert, find and remove fields with ServerTextControl: TextField, MS Word application fields, hypertext links, bookmarks, field adapters and conversion to text.

- **Product:** TX Text Control .NET Server
- **Section:** Documentation
- **Kind:** Topic
- **Path:** TX Text Control .NET Server > Document Processing > Fields
- **8315 words**
- **Web URL:** https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/fields/
- **LLMs URL:** https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/fields/llms.txt
- **LLMs-Full URL:** https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/fields/llms-full.txt

---

Fields mark the parts of a document that code finds and changes later: a customer name, a link to a website, a bookmark, a Word merge field. On the server, you insert these fields, find them in the main text, headers, footers and text frames, change and remove them and turn them into plain text before a document leaves your application.

Merge fields that `MailMerge` fills with data are covered in [Merge Fields](https://docs.textcontrol.com/tx-text-control-dotnet-server/getting-started/mail-merge/fields/llms-full.txt), and the content controls of MS Word forms in [Content Controls](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/content-controls/llms-full.txt). Every program below replaces the content of *Program.cs* in a console application.

### The Kinds of Fields

A field is a marked piece of text with properties such as a name. Each kind of field has a collection of its own:

| Field | Collection of `ServerTextControl` | Used for |
|---|---|---|
| [TextField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/llms-full.txt) | [TextFields](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/textfields-property/llms-full.txt) | Text that your code identifies by its name or ID |
| [ApplicationField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/applicationfield/llms-full.txt) | [ApplicationFields](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/applicationfields-property/llms-full.txt) | Fields of MS Word, such as `MERGEFIELD`, `IF` and `DATE` |
| [HypertextLink](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/hypertextlink/llms-full.txt) | [HypertextLinks](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/hypertextlinks-property/llms-full.txt) | Links to a website or another document |
| [DocumentTarget](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/documenttarget/llms-full.txt) | [DocumentTargets](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/documenttargets-property/llms-full.txt) | Bookmarks, positions that links point to |
| [DocumentLink](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/documentlink/llms-full.txt) | [DocumentLinks](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/documentlinks-property/llms-full.txt) | Links to a bookmark in the same document |
| [PageNumberField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/pagenumberfield/llms-full.txt) | `HeaderFooter.PageNumberFields` | Page numbers in headers and footers, described in [Headers and Footers](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/headers-footers/llms-full.txt) |
| [FormField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/formfield/llms-full.txt) | [FormFields](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/formfields-property/llms-full.txt) | Form fields that users fill out, described in [Form Fields](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/form-fields/llms-full.txt) |

Keep these points in mind:

- **Main text only.** The collections of `ServerTextControl` contain the fields of the main text. Headers, footers and text frames have the same collections for their own fields.
- **Word fields need a load setting.** Fields of MS Word documents are imported as application fields only when `LoadSettings.ApplicationFieldFormat` is set before loading, as [Load a Document](https://docs.textcontrol.com/tx-text-control-dotnet-server/getting-started/document-processing/load/#load-word-templates-with-fields) shows.
- **Several kinds at once.** [GetTextFields](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/gettextfields-method/llms-full.txt) returns the fields of the kinds you combine from [TextFieldType](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfieldtype/enumeration/llms-full.txt), such as `TextFieldType.HypertextLink | TextFieldType.DocumentLink`.

### Insert a Text Field

A text field is inserted at the current input position. The following program writes a label and inserts a field with the customer name behind it:

```csharp
using TXTextControl;

using (ServerTextControl tx = new ServerTextControl())
{
    tx.Create();

    tx.Selection.Text = "Customer: ";

    // A name and an ID let your code find the field again
    TextField customerField = new TextField("Acme Corporation")
    {
        Name = "CustomerName",
        ID = 1
    };

    if (tx.TextFields.CanAdd && tx.TextFields.Add(customerField))
    {
        Console.WriteLine($"Field inserted at position {customerField.Start}");
    }

    tx.Save("fields.tx", StreamType.InternalUnicodeFormat);
}
```

The code works as follows:

- The [TextField constructor](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/constructor/llms-full.txt) takes the text of the field.
- [Name](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/name-property/llms-full.txt) is any text, and [ID](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/id-property/llms-full.txt) a number. Both are saved with the document and identify the field later.
- [CanAdd](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfieldcollectionbase/canadd-property/llms-full.txt) tells whether a field can be inserted at the input position; a field can't be inserted into another field. [Add](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfieldcollection/add-method/llms-full.txt) returns `true` if the field was inserted.
- [Start](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/start-property/llms-full.txt) is the one-based position of the field's first character.
- Text fields are kept in the TX Text Control format, so the document is saved as *fields.tx*.

`Name` has no length limit, so a field can carry a larger piece of data, such as a JSON string, along with its text.

#### Set How Users Edit the Field

The following properties are saved with the document and take effect when a user edits it later, for example in the [Document Editor](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-editor/fields/llms-full.txt):

- [Editable](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/editable-property/llms-full.txt) decides whether users can change the text of the field, and [Deleteable](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/deleteable-property/llms-full.txt) whether they can delete it. A field that isn't deleteable keeps its text editable, but a selection with the field inside can't be deleted or replaced.
- [DoubledInputPosition](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/doubledinputposition-property/llms-full.txt) adds a second input position in front of the first and behind the last character of the field, so that users decide whether text typed at the edge belongs to the field. It's `false` by default and always `true` for form fields.
- [HighlightMode](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/highlightmode-property/llms-full.txt) decides when the field is shown with a colored background. With `HighlightMode.Activated`, the field is highlighted while the input position is inside it, where the next typed character becomes part of the field. [HighlightColor](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/highlightcolor-property/llms-full.txt) sets the color; its default is black with an alpha value of 60, a light gray.

```csharp
TextField priceField = new TextField("$ 22.45")
{
    Name = "Price",
    DoubledInputPosition = true,
    HighlightMode = HighlightMode.Activated
};

tx.TextFields.Add(priceField);
```

### Add Hypertext Links and Bookmarks

A hypertext link points to a website or another document. A bookmark, a [DocumentTarget](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/documenttarget/llms-full.txt), marks a position, and a document link points to it. The following program adds all three to one paragraph:

```csharp
using TXTextControl;

using (ServerTextControl tx = new ServerTextControl())
{
    tx.Create();

    tx.Text = "Terms and Conditions. The current version is published on . If you have questions, read ";

    // A bookmark in front of the first character
    tx.Select(0, 0);
    DocumentTarget termsTarget = new DocumentTarget("terms");
    tx.DocumentTargets.Add(termsTarget);

    // A hypertext link behind "published on "
    tx.Select(tx.Text.IndexOf("published on ") + "published on ".Length, 0);
    HypertextLink website = new HypertextLink("our website", "https://www.textcontrol.com/")
    {
        DescriptiveText = "Text Control website"
    };
    tx.HypertextLinks.Add(website);

    // A link to the bookmark at the end of the text
    tx.Select(tx.Text.Length, 0);
    tx.DocumentLinks.Add(new DocumentLink("the terms", termsTarget));

    tx.Save("links.tx", StreamType.InternalUnicodeFormat);
}
```

The code works as follows:

- `Select` with a length of 0 sets the input position, where each field is inserted. The text has a single paragraph, so a position in the string is the position in the document.
- The [DocumentTarget constructor](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/documenttarget/constructor/llms-full.txt) takes the name of the bookmark.
- The [HypertextLink constructor](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/hypertextlink/constructor/llms-full.txt) takes the text of the link and its target, which [Target](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/hypertextlink/target-property/llms-full.txt) reads and changes later. [DescriptiveText](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/hypertextlink/descriptivetext-property/llms-full.txt) describes the link in accessible PDF documents.
- The [DocumentLink constructor](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/documentlink/constructor/llms-full.txt) takes the text of the link and the `DocumentTarget` it points to.

### Find the Fields of All Text Parts

To find every field of a document, including those in headers, footers and text frames, loop through [ServerTextControl.TextParts](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/textparts-property/llms-full.txt). Each text part implements [IFormattedText](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/iformattedtext/llms-full.txt), which has the field collections:

```csharp
using TXTextControl;

LoadSettings loadSettings = new LoadSettings()
{
    ApplicationFieldFormat = ApplicationFieldFormat.MSWord
};

using (ServerTextControl tx = new ServerTextControl())
{
    tx.Create();
    tx.Load("Documents/sample.docx", StreamType.WordprocessingML, loadSettings);

    foreach (IFormattedText textPart in tx.TextParts)
    {
        // MainText, TextFrame, HeaderFooter or FootnoteText
        string part = textPart.GetType().Name;

        foreach (ApplicationField field in textPart.ApplicationFields)
        {
            string parameters = field.Parameters != null ? string.Join(" ", field.Parameters) : "";
            Console.WriteLine($"{part}: {field.TypeName} {parameters} = \"{field.Text}\"");
        }

        foreach (HypertextLink link in textPart.HypertextLinks)
        {
            Console.WriteLine($"{part}: link to {link.Target} = \"{link.Text}\"");
        }

        foreach (DocumentTarget target in textPart.DocumentTargets)
        {
            Console.WriteLine($"{part}: bookmark {target.TargetName}");
        }
    }
}
```

The text parts come in a fixed order: the main text first, then the text frames and then the headers and footers. For an application field, [TypeName](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/applicationfield/typename-property/llms-full.txt) is the Word field type, such as `MERGEFIELD`, and [Parameters](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/applicationfield/parameters-property/llms-full.txt) holds the rest of the field code: for `MERGEFIELD Address \* Upper \v`, the three elements `Address`, `\* Upper` and `\v`.

#### Field Formats and Type Names

The field formats of different applications aren't compatible, so [LoadSettings.ApplicationFieldFormat](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/loadsettings/applicationfieldformat-property/llms-full.txt) names the one to import. [ApplicationFieldFormat](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/applicationfieldformat/enumeration/llms-full.txt) has these values:

| Value | Imports |
|---|---|
| `None` | No application fields |
| `MSWord` | The fields of MS Word, including its legacy form fields and content controls |
| `MSWordTXFormFields` | The form fields of MS Word as TX Text Control form fields, the other Word fields as application fields, described in [Content Controls](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/content-controls/llms-full.txt) |
| `HighEdit` | The fields of the Heiler HighEdit component in RTF documents |

[LoadSettings.ApplicationFieldTypeNames](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/loadsettings/applicationfieldtypenames-property/llms-full.txt) limits the import to the type names you list, such as `new string[] { "MERGEFIELD", "PRINTDATE" }`. Besides the field names of MS Word, two groups of type names hold their settings as Office Open XML markup in `Parameters` rather than as switches:

| Type name | Word element | What `Parameters` holds |
|---|---|---|
| `FORMCHECKBOX`, `FORMDROPDOWN`, `FORMTEXT` | The legacy form fields: check box, drop-down list and text box | The options of Word's **Form Field Options** dialog box |
| `SDTBLOCK` | A content control | Its properties; the `w:val` attribute of the `w:tag` element names the kind of control: rich text, plain text, picture, combo box, drop-down list or check box |

The [FormText](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/formtext/llms-full.txt), [FormCheckBox](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/formcheckbox/llms-full.txt) and [FormDropDown](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/formdropdown/llms-full.txt) adapters and the content control adapters in [Use Field Adapters for MS Word Fields](#use-field-adapters-for-ms-word-fields) read this markup for you.

### Change and Remove Fields

The collections have the same methods for all kinds of fields. `GetItem` with an ID returns a field or `null`, and `Remove` removes a field, with or without its text. A collection can't be changed while a `foreach` loop runs over it, so collect the fields to remove first:

```csharp
using TXTextControl;

using (ServerTextControl tx = new ServerTextControl())
{
    tx.Create();
    tx.Load("fields.tx", StreamType.InternalUnicodeFormat);

    // Change the text of a field by its name
    foreach (TextField field in tx.TextFields)
    {
        if (field.Name == "CustomerName")
        {
            field.Text = "Text Control, LLC";
        }
    }

    // Remove the field with the ID 1 and keep its text
    TextField fieldWithId = tx.TextFields.GetItem(1);

    if (fieldWithId != null)
    {
        tx.TextFields.Remove(fieldWithId, true);
    }

    // Collect the merge fields first, then remove them with their text
    List<ApplicationField> mergeFields = new List<ApplicationField>();

    foreach (ApplicationField field in tx.ApplicationFields)
    {
        if (field.TypeName == "MERGEFIELD")
        {
            mergeFields.Add(field);
        }
    }

    foreach (ApplicationField field in mergeFields)
    {
        tx.ApplicationFields.Remove(field, false);
    }

    tx.Save("fields-changed.tx", StreamType.InternalUnicodeFormat);
}
```

[TextFieldCollection.GetItem](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfieldcollection/getitem-method/llms-full.txt) without a parameter returns the field at the input position. [Remove](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfieldcollection/remove-method/llms-full.txt) with `true` as second parameter removes the field and keeps its text; without it, or with `false`, the text is removed too.

#### Change the Parameters of a Word Field

`Parameters` returns a .NET array, which has a fixed size. To add or remove a switch, build a new array and assign it to the property. The following program removes the `\v` switch from every merge field and sets the text the `Address` field shows:

```csharp
using TXTextControl;

LoadSettings loadSettings = new LoadSettings()
{
    ApplicationFieldFormat = ApplicationFieldFormat.MSWord
};

using (ServerTextControl tx = new ServerTextControl())
{
    tx.Create();
    tx.Load("Documents/sample.docx", StreamType.WordprocessingML, loadSettings);

    foreach (ApplicationField field in tx.ApplicationFields)
    {
        if (field.TypeName != "MERGEFIELD" || field.Parameters == null)
        {
            continue;
        }

        // A new array without the \v switch replaces the old one
        if (Array.IndexOf(field.Parameters, "\\v") >= 0)
        {
            field.Parameters = field.Parameters.Where(p => p != "\\v").ToArray();
        }

        // The first parameter of a MERGEFIELD is the field name
        if (field.Parameters.Length > 0 && field.Parameters[0] == "Address")
        {
            field.Text = "221B Baker Street, London";
        }
    }

    tx.Save("sample-fields.docx", StreamType.WordprocessingML);
}
```

The code works as follows:

- `"\\v"` in C# is the two characters `\v` of the Word switch. A single backslash would be the vertical tab character.
- `Where` and `ToArray` create a new array; assigning it to [Parameters](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/applicationfield/parameters-property/llms-full.txt) changes the field code.
- Setting `Text` changes what the field shows, not its type or parameters.

#### React to Created and Deleted Fields

[TextFieldCreated](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/textfieldcreated-event/llms-full.txt) and [TextFieldDeleted](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/servertextcontrol/textfielddeleted-event/llms-full.txt) occur for fields of every class, and [TextFieldEventArgs.TextField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfieldeventargs/textfield-property/llms-full.txt) holds the field:

- **Created.** Names and IDs are saved and copied with a field, so a copy has the same name as the original. The handler of `TextFieldCreated` is the place to give a new field a name or ID of its own, such as "Copy of Price" for a second "Price" field.
- **Deleted.** After a field has been deleted, only its `ID` and `Name` are valid. Identify the removed field by them and don't read its text or position.

```csharp
tx.TextFieldDeleted += (sender, e) =>
{
    // Only ID and Name of a deleted field are valid
    Console.WriteLine($"Field removed: {e.TextField.Name} ({e.TextField.ID})");
};
```

[Events](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/events/llms-full.txt) lists these events with the other events of `ServerTextControl`.

### Show Field Codes

MS Word can show a field as its field code, such as `{ MERGEFIELD Total \# "#,##0.00" }`, instead of its text. TX Text Control has no switch for this, but the code can be built from the field's `TypeName` and `Parameters` and set as the field's text. A proof copy of a template that shows every field code helps authors check field names and formats. The following program shows the codes of the merge fields in a small template, saves the proof as PDF, puts the original texts back and saves the template:

```csharp
using TXTextControl;
using TXTextControl.DocumentServer.Fields;

using (ServerTextControl tx = new ServerTextControl())
{
    tx.Create();

    // A template with two merge fields
    tx.Selection.Text = "Dear ";
    MergeField name = new MergeField() { Name = "CustomerName", Text = "«CustomerName»" };
    tx.ApplicationFields.Add(name.ApplicationField);

    tx.Selection.Text = ",\r\nyour order total is ";
    MergeField total = new MergeField() { Name = "Total", Text = "«Total»", NumericFormat = "#,##0.00", TextAfter = " USD" };
    tx.ApplicationFields.Add(total.ApplicationField);
    tx.Selection.Text = ".";

    // Show the field codes and remember the field texts
    List<(ApplicationField Field, string Text)> fieldTexts = new List<(ApplicationField, string)>();

    foreach (ApplicationField field in tx.ApplicationFields)
    {
        fieldTexts.Add((field, field.Text));
        field.Text = "{ " + field.TypeName + " " + string.Join(" ", field.Parameters) + " }";
    }

    tx.Save("template-field-codes.pdf", StreamType.AdobePDF);

    // Show the field texts again
    foreach ((ApplicationField field, string text) in fieldTexts)
    {
        field.Text = text;
    }

    tx.Save("template.docx", StreamType.WordprocessingML);
}
```

The PDF shows the two lines as `Dear { MERGEFIELD CustomerName },` and `your order total is { MERGEFIELD Total \f " USD" \# "#,##0.00" }.`: the [MergeField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/mergefield/llms-full.txt) adapter stores the text after the field and the number format as the switches `\f` and `\#`. Changing [TextField.Text](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/textfield/text-property/llms-full.txt) changes only what the field shows; its type and parameters stay, so the restored template still contains both merge fields. For templates loaded from DOCX files, set `ApplicationFieldFormat` as in the section above. The blog article [Toggle Field Codes in TX Text Control](https://www.textcontrol.com/blog/2024/11/07/toggle-field-codes-in-tx-text-control/) toggles the codes of a single field, also in the Document Editor.

### Convert Fields to Plain Text

Before a document is sent to a customer, its fields can be removed while their visible text stays. `Clear(true)` does this for all fields of a collection:

```csharp
using TXTextControl;

LoadSettings loadSettings = new LoadSettings()
{
    ApplicationFieldFormat = ApplicationFieldFormat.MSWord
};

using (ServerTextControl tx = new ServerTextControl())
{
    tx.Create();
    tx.Load("Documents/sample.docx", StreamType.WordprocessingML, loadSettings);

    foreach (IFormattedText textPart in tx.TextParts)
    {
        // true removes the fields and keeps their text
        textPart.ApplicationFields.Clear(true);
        textPart.TextFields.Clear(true);
        textPart.HypertextLinks.Clear(true);
        textPart.DocumentLinks.Clear(true);

        // Bookmarks have no text of their own
        textPart.DocumentTargets.Clear();
    }

    tx.Save("sample-plain.docx", StreamType.WordprocessingML);
}
```

[ApplicationFieldCollection.Clear](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/applicationfieldcollection/clear-method/llms-full.txt) and the `Clear` methods of the other collections take `keepText` as parameter. [DocumentTargetCollection.Clear](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol/documenttargetcollection/clear-method/llms-full.txt) takes none.

### Use Field Adapters for MS Word Fields

An `ApplicationField` only gives access to the type name, parameters and text of a Word field; the logic of the field isn't implemented. The classes of the `TXTextControl.DocumentServer.Fields` namespace are adapters for typical Word fields: they wrap an application field and give typed access to its settings, so you don't have to know the syntax of the field code.

- **Change an existing field:** pass the application field to the adapter's constructor, for example `new MergeField(applicationField)`.
- **Create a new field:** create the adapter, set its properties and add its `ApplicationField` to a collection, for example `tx.ApplicationFields.Add(mergeField.ApplicationField)`.

| Adapter | Field | Described in |
|---|---|---|
| [MergeField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/mergefield/llms-full.txt) | `MERGEFIELD` | [Merge Fields](https://docs.textcontrol.com/tx-text-control-dotnet-server/mail-merge/fields/llms-full.txt) |
| [DateField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/datefield/llms-full.txt) | `DATE`, the current date in a format | [Merge Fields](https://docs.textcontrol.com/tx-text-control-dotnet-server/mail-merge/fields/llms-full.txt) |
| [IfField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/iffield/llms-full.txt) | `IF`, text that depends on a comparison | [Conditional Content](https://docs.textcontrol.com/tx-text-control-dotnet-server/mail-merge/conditional-content/llms-full.txt) |
| [IncludeText](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/includetext/llms-full.txt) | `INCLUDETEXT`, another document included in a template | [Template Design](https://docs.textcontrol.com/tx-text-control-dotnet-server/mail-merge/template-design/llms-full.txt) |
| [NextField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/nextfield/llms-full.txt), [NextIfField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/nextiffield/llms-full.txt) | `NEXT` and `NEXTIF`, which advance to the next data record | [Overview](https://docs.textcontrol.com/tx-text-control-dotnet-server/mail-merge/overview/#put-several-records-on-one-page), [Conditional Content](https://docs.textcontrol.com/tx-text-control-dotnet-server/mail-merge/conditional-content/#move-to-the-next-record-conditionally) |
| [FormText](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/formtext/llms-full.txt), [FormCheckBox](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/formcheckbox/llms-full.txt), [FormDropDown](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/formdropdown/llms-full.txt) | The legacy form fields of MS Word | — |
| [ContentControlFieldAdapter](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/contentcontrolfieldadapter/llms-full.txt) and its derived classes | The content controls of MS Word | [Content Controls](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/content-controls/llms-full.txt) |

All adapters derive from [FieldAdapter](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/fieldadapter/llms-full.txt), whose [ApplicationField](https://docs.textcontrol.com/tx-text-control-dotnet-server/reference/txtextcontrol-documentserver-fields/fieldadapter/applicationfield-property/llms-full.txt) property returns the wrapped field. The blog article [Find ApplicationFields within Sections and Paragraphs in .NET C#](https://www.textcontrol.com/blog/2024/08/02/find-applicationfields-within-sections-and-paragraphs-in-net-c-sharp/) finds the fields of a particular section or paragraph by comparing positions.

### Next Steps

- [Content Controls](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/content-controls/llms-full.txt): read and fill the content controls of MS Word forms.
- [Merge Fields](https://docs.textcontrol.com/tx-text-control-dotnet-server/mail-merge/fields/llms-full.txt): fill merge fields with data.
- [Headers and Footers](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/headers-footers/llms-full.txt): add page number fields.
- [Fields](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-editor/fields/llms-full.txt) in the Document Editor: insert and change fields from JavaScript.

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## Nearby

- **Previous:** [Tables of Contents](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/tables-of-contents/llms-full.txt)
- **Next:** [Subtext Parts](https://docs.textcontrol.com/tx-text-control-dotnet-server/document-processing/subtext-parts/llms-full.txt)