C# .NET - how can i validate textbox control in window application

help me to  validate the numbers, letters and email id's

end of post

script language = "Javascript">
/**
 * DHTML email validation script. Courtesy of SmartWebby.com (http://www.smartwebby.com/dhtml/)
 */

function echeck(str) {

  var at="@"
  var dot="."
  var lat=str.indexOf(at)
  var lstr=str.length
  var ldot=str.indexOf(dot)
  if (str.indexOf(at)==-1){
     alert("Invalid E-mail ID")
     return false
  }

  if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
     alert("Invalid E-mail ID")
     return false
  }

  if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
      alert("Invalid E-mail ID")
      return false
  }

   if (str.indexOf(at,(lat+1))!=-1){
      alert("Invalid E-mail ID")
      return false
   }

   if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
      alert("Invalid E-mail ID")
      return false
   }

   if (str.indexOf(dot,(lat+2))==-1){
      alert("Invalid E-mail ID")
      return false
   }
  
   if (str.indexOf(" ")!=-1){
      alert("Invalid E-mail ID")
      return false
   }

    return true     
 }

function ValidateForm(){
 var emailID=document.frmSample.txtEmail
 
 if ((emailID.value==null)||(emailID.value=="")){
  alert("Please Enter your Email ID")
  emailID.focus()
  return false
 }
 if (echeck(emailID.value)==false){
  emailID.value=""
  emailID.focus()
  return false
 }
 return true
 }
</script>

check this link

http://www.smartwebby.com/DHTML/phone_no_validation.asp

 

using System.Text.RegularExpressions;

string pattern = @"^[a-z][a-z|0-9|]*([_][a-z|0-9]+)*([.][a-z|" +

@"0-9]+([_][a-z|0-9]+)*)?@[a-z][a-z|0-9|]*\.([a-z]" +

@"[a-z|0-9]*(\.[a-z][a-z|0-9]*)?)$";

System.Text.RegularExpressions.Match match =

Regex.Match(email, pattern, RegexOptions.IgnoreCase);

if (!match.Success)

{

// error in address

}

http://social.microsoft.com/Forums/en-US/netfxnetcom/thread/c3c4130b-d2a1-4ad1-a24c-dcf3cab3070b

 Numbers:

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{

if (!Char.IsNumber(e.KeyChar))
{
MessageBox.Show("PLease Enter Numeric Value");
e.Handled = true ;
}
}

Email:

To validate a email id in textbox you can place this code in Validating event of textbox or in Leave event of textbox and make use of  the regex classes which are located in the namespace System.Text.RegularExpressions

 System.Text.RegularExpressions.Regex rEMail = new System.Text.RegularExpressions.Regex(@"^[a-zA-Z][\w\.-]{2,28}[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$");

            if (txtmail.Text.Length > 0){

                if (!rEMail.IsMatch(txtmail.Text))
                {
                    MessageBox.Show("E-Mail expected", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    txtmail.SelectAll();
                    e.Cancel = true;
                }

using system.Text;
// validation for letters
RegularExpressions.Regex RegExp = new RegularExpressions.Regex(@"^[a-zA-Z]$");

            if (txtInput.Text.Length > 0){

                if (!RegExp .IsMatch(txtInput.Text))
                {
                    MessageBox.Show("Enter valid data");
                    txtInput.focus();
                 }

}

Validation for number
RegularExpressions.Regex RegExp = new RegularExpressions.Regex(@"^[0-9]$");

Validation for email:
RegularExpressions.Regex RegExp = new RegularExpressions.Regex(@"
^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]\                               .)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$")

Try this link,