1. In MVC3 Razor we have HTML helpers to render different controls. 
2. Instead of using these helpers we can create our own helper classes and methods and use them as we want.
3. The creation of custom helpers provides flexibility to change the attributes and style of the control that renders.
4. In this article we will create Custom HTML helper for TextBox to render TextBox control.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;

namespace CustomHtmlHelpers.CustomHelpers
{
    public static class CustomTextBoxHelper
    {

        public static MvcHtmlString Custom_TextBox(this HtmlHelper helper, string name)
        {
            return Custom_TextBox(helper, name, null, null);
        }

        public static MvcHtmlString Custom_TextBox(this HtmlHelper helper, string name,string text)
        {
            return Custom_TextBox(helper, name, text, null);
        }

        public static MvcHtmlString Custom_TextBox(this HtmlHelper helper, string name, string text, object htmlAttributes)
        {
            TagBuilder textBox = new TagBuilder("input");
            textBox.Attributes.Add("type", "text");
            textBox.Attributes.Add("name", name);
            textBox.Attributes.Add("id", name);

            if (!string.IsNullOrEmpty(text))
            {
                textBox.Attributes.Add("value", text);
            }

            textBox.MergeAttributes(new RouteValueDictionary(htmlAttributes));
            return MvcHtmlString.Create(textBox.ToString(TagRenderMode.Normal));
        }
    }
}

In the above example, we have created a static class. We have created three overloads accepting different number of parameters to support multiple requirements.

Overload 1 : The first overload accepts name parameter. This name parameter is used to set the id and name attribute. This method is extension method and accepts object of HtmlHelper class. The first parameter adds this overload to System.Web.MVC namespace. On view we can access this method using @html. This overload in turn calls another overload.

Overload 2 : The second overload accepts name and text as parameters. The name is used to set name attribute and text is used to set the value attribute of textbox. This overload calls another overload.

Overload 3 : The third overload accepts name, text and htmlAttributes object. The htmlAttributes object contains route values passed from the view. In this method we are creating a input element using TagBuilder class, we are setting its type attribute to test to render textbox. We are also setting name, id, value and any other attributes passed using htmlAttributes.


View :

    <input id="CustomText" name="CustomText" type="text"></input>

    <input id="CustomText" name="CustomText" type="text" value="Hello World"></input>

    <input id="CustomText" name="CustomText" style="color:Red;" type="text" value="Hello World"></input>

This is how we can create a Custom TextBox Helper in MVC3 Razor and fulfill our specific project needs.