how to count lowercase letter in Textbox

Hi,

You can count using RegEx.

using System.IO;
using System;
using System.Text.RegularExpressions;

class Program
{
static void Main()
{
string strRegex = @"(?<=[a-z])";
RegexOptions myRegexOptions = RegexOptions.Multiline;
Regex myRegex = new Regex(strRegex, myRegexOptions);
string strTargetString = @"ADGFesD";

Console.WriteLine("The string has " + myRegex.Matches(strTargetString).Count + " lowercase letters");
}
}