---
title: "C# .NET PDF form library: Create, fill, and extract | Nutrient .NET SDK"
canonical_url: "https://www.nutrient.io/guides/dotnet/forms/fill-form-fields/programmatic/"
md_url: "https://www.nutrient.io/guides/dotnet/forms/fill-form-fields/programmatic.md"
last_updated: "2026-05-21T17:12:02.203Z"
description: "Learn how to work with PDF forms programmatically in C# .NET using Nutrient .NET SDK. Fill, extract, and manipulate form data within your applications."
---

# C# .NET PDF form library

The guide explains how to fill form fields programmatically in a PDF document. This feature enables you to, for example, fill in many forms in one go with values from a database.

To fill form fields programmatically in a PDF document, follow the steps below:

1. Create a `GdPicturePDF` object.

2. Determine the number of form fields in the document with the `GetFormFieldsCount` method.

3. Loop through the form fields.

4. For each form field, determine the title with the `GetFormFieldId` and `GetFormFieldTitle` methods.

5. If the title matches your conditions, such as family or given name, set a value for the form field with the `SetFormFieldValue` method.

6. Save the output in a new PDF file with the `SaveToFile` method.

The code below opens a fillable PDF document, fills in two form fields, and saves the output in a new PDF file:

### C#

```csharp

using GdPicturePDF gdpicturePDF = new GdPicturePDF();
// Load the source document.
gdpicturePDF.LoadFromFile(@"C:\temp\source.pdf");
// Determine the number of form fields.
int formFieldCount = gdpicturePDF.GetFormFieldsCount();
// Loop through the form fields.
for (int formFieldIndex = 0; formFieldIndex <= formFieldCount - 1; formFieldIndex++)
{
    // Determine the title of the form field.
    int formFieldId = gdpicturePDF.GetFormFieldId(formFieldIndex);
    string formFieldTitle = gdpicturePDF.GetFormFieldTitle(formFieldId);
    // Set a value for the form field.
    if (formFieldTitle== "Family Name")
    {
        gdpicturePDF.SetFormFieldValue(formFieldId, "Doe");
    }
    else if (formFieldTitle == "Given Name")
    {
        gdpicturePDF.SetFormFieldValue(formFieldId, "Jane");
    }
}
// Save the output in a new PDF file.
gdpicturePDF.SaveToFile(@"C:\temp\output.pdf");

```

### VB.NET

```vb

Using gdpicturePDF As GdPicturePDF = New GdPicturePDF()
    ' Load the source document.
    gdpicturePDF.LoadFromFile("C:\temp\source.pdf")
    ' Determine the number of form fields.
    Dim formFieldCount As Integer = gdpicturePDF.GetFormFieldsCount()
    ' Loop through the form fields.
    For formFieldIndex = 0 To formFieldCount - 1
        ' Determine the title of the form field.
        Dim formFieldId As Integer = gdpicturePDF.GetFormFieldId(formFieldIndex)
        Dim formFieldTitle As String = gdpicturePDF.GetFormFieldTitle(formFieldId)
        ' Set a value for the form field.
        If Equals(formFieldTitle, "Family Name") Then
            gdpicturePDF.SetFormFieldValue(formFieldId, "Doe")
        ElseIf Equals(formFieldTitle, "Given Name") Then
            gdpicturePDF.SetFormFieldValue(formFieldId, "Jane")
        End If
    Next
    ' Save the output in a new PDF file.
    gdpicturePDF.SaveToFile("C:\temp\output.pdf")
End Using

```

#### Used Methods and Properties

- [`GetFormFieldId`](/api/gdpicture/GdPicture.NET.14.API~GdPicture14.GdPicturePDF~GetFormFieldId.html)

- [`GetFormFieldsCount`](/api/gdpicture/GdPicture.NET.14.API~GdPicture14.GdPicturePDF~GetFormFieldsCount.html)

- [`GetFormFieldTitle`](/api/gdpicture/GdPicture.NET.14.API~GdPicture14.GdPicturePDF~GetFormFieldTitle.html)

- [`LoadFromFile`](/api/gdpicture/GdPicture.NET.14.API~GdPicture14.GdPicturePDF~LoadFromFile.html)

- [`SaveToFile`](/api/gdpicture/GdPicture.NET.14.API~GdPicture14.GdPicturePDF~SaveToFile.html)

- [`SetFormFieldValue`](/api/gdpicture/GdPicture.NET.14.API~GdPicture14.GdPicturePDF~SetFormFieldValue.html)

#### Related Topics

- [Load a File](/guides/dotnet/load-a-file.md)

- [Save a File](/guides/dotnet/save-a-file.md)

---

## Related pages

- [Import XFDF data into PDF forms using C#](/guides/dotnet/forms/fill-form-fields/import-from-database.md)
- [Fill PDF forms using XFDF in C# .NET](/guides/dotnet/forms/fill-form-fields/import-from-xfdf.md)
- [C# .NET PDF Form Library](/guides/dotnet/forms/fill-form-fields/add-image.md)
- [C# .NET PDF Form Library](/guides/dotnet/forms/fill-form-fields/attach-file.md)