Prepopulate/Prefill WFFM Form’s field Sitecore.

We need to create custom control then we can pre-fill/databind our WFFM form.

Here we are adding custom SingleLineTextField. Below are steps:

1) Create custom control designer class, where we can add our custom property

namespace xxx.Foundation.Forms.WFFM
{
    [Designer("System.Windows.Forms.Design.ParentControlDesigner, System.Design", typeof(IDesigner))]
    public class CustomTextBox : RegexInputControl
    {
        private static readonly string baseCssClassName = "scfSingleLineTextBorder";
        [VisualCategory("Custom Properties")]
        [VisualProperty("Identifier", 2)]
        [DefaultValue("")]
        public string Identifier { get; set; }
        [VisualCategory("Validation"), VisualProperty("Minimum Length:", 1000), DefaultValue(0)]
        public int MinLength
        {
            get;
            set;
        }
        [VisualProperty("Maximum Length:", 2000)]
        [DefaultValue(256)]
        [VisualCategory("Validation")]
        public int MaxLength
        {
            get
            {
                return this.textbox.MaxLength;
            }
            set
            {
                this.textbox.MaxLength = value;
            }
        }
        [VisualProperty("CSS Class:", 600)]
        [VisualFieldType(typeof(CssClassField))]
        [DefaultValue("scfSingleLineTextBorder")]
        public new string CssClass
        {
            get
            {
                return base.CssClass;
            }
            set
            {
                base.CssClass = value;
            }
        }
        public CustomTextBox(HtmlTextWriterTag tag): base(tag)
        {
            this.MaxLength = 256;
            this.MinLength = 0;

2) Create MVC Type class to data-bind custom control. Here we can apply our binding logic.

namespace xxx.Foundation.Forms.WFFM
    {
        public class CustomTextBoxMVC : SingleLineTextField
        {
            public CustomTextBoxMVC()
            {

            }

            public override void Initialize()
            {
                //Here can do data-bind 
                this.Value = "My Value";
            }
        }
    }

3) Go to below path and add new field type.

/sitecore/system/Modules/Web Forms for Marketers/Settings/Field Types/Custom/

Here in this example we are adding CustomTextBox. Specified Assembly,Class,MVC Type field under Data section.

4) WFFM form designer choose newly created custom control.