Adding a Primary Key Constraint on Column

  ALTER TABLE employee ADD CONSTRAINT emp_id_pk PRIMARY KEY(emp_id)

Increasing the width of a column

  ALTER TABLE employee ALTER COLUMN emp_name varchar(100)

Decreasing the width of a column

  ALTER TABLE employee ALTER COLUMN emp_name varchar(50)

Changing the Data Type of Column

  ALTER TABLE employee ALTER COLUMN emp_name nvarchar(50)

Add a NULL Constraint on Column

  ALTER TABLE employee ALTER COLUMN emp_name nvarchar(50) NULL

Add a NOT NULL Constraint on Column

  ALTER TABLE employee ALTER COLUMN emp_name nvarchar(50) NOT NULL

Add a new Column on Table without any Constraint

  ALTER TABLE employee ADD emp_age varchar(10)

Add a new Column on Table with a Constraint

  ALTER TABLE employee ADD emp_code varchar(100) CONSTRAINT emp_code_uq UNIQUE

Drop a Column from Table

  ALTER TABLE employee DROP COLUMN emp_code

Adding a Check Constraint Column

  ALTER TABLE employee ADD CONSTRAINT emp_age_ck (emp_age > 18)


Here is the our aspx page that contains a JavaScript method and a hidden filed and button.
<script type="text/javascript">
  function SetValue() {
    var sValue = "Hello World";
    document.getElementById("Hidden1").value = str;
  }
</script>
<html>
  <head>
    <title>How to set c# variable value in javascript</title>
  </head>
  <body>
    <div>
      <asp:hiddenfield id="hdnVlaue" runat="server"></asp:hiddenfield>
      <asp:button id="btnClick" runat="server" onclientclick="SetValue()" onclick="&rdquo;" text="Click Me">         </asp:button>
    </div>
   </body>
</html>

Now in the click event of the btnClick, we will set value received by JavaScript function

protected void btnClick_Click(object sender, EventArgs e)
{
  string sValue = hdnVlaue.Value;
  Response.Write("The Received Value is " + sValue);


}
using System;
using System.Net.Mail;
using System.Net.Security;
public partial class SendEmailPage : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        MailMessage oMailMessage = new MailMessage("Your Email Address ", "Recepent’s Email Address ");
        oMailMessage.Subject = "Write Your Mail Here";
        oMailMessage.Body = "Write Your Email Message";
        oMailMessage.IsBodyHtml = false;
        SmtpClient oSmtpClient = new SmtpClient("smtp.gmail.com", 587);
        oSmtpClient.Credentials = new System.Net.NetworkCredential("Email Username", "Email Password");
        oSmtpClient.EnableSsl = true;
        oSmtpClient.Send(oMailMessage);
    }
}


using System;
using System.Web;
using System.Web.UI;

public partial class GetDeviceType : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected override void OnInit(EventArgs e)
    {
        string sUserAgent = Request.UserAgent.ToLower();
        if (sUserAgent.Contains("tablet"))
        {
            this.MasterPageFile = "/Tablet.master";
        }
        else
        {
            this.MasterPageFile = "/Mobile.master";
        }
    }

}