How do I pass an HTML element's value to a C# code-behind method?

Answer 1

If you want to pass a value from client-side to code behind without posting back the entire page, you will need to use Ajax.

Calling to a server-side method in ASP.Net Web Form is not as clean as ASP.Net Web API or MVC. You will need to use old WebMethod.

For example,

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="DemoWebForm.Default" %>





    


    
        Get Data
        

        
        
        
    

Code Behind

using System;
using System.Web.Script.Serialization;

namespace DemoWebForm
{
    public partial class Default : System.Web.UI.Page
    {
        [System.Web.Services.WebMethod]
        public static string GetCurrentDate(string value)
        {
            return new JavaScriptSerializer().Serialize(
                string.Format("{0} - {1}", DateTime.Now, value));
        }
    }
}