How to find Upper Case Letter in String

Question

Sir Actually i want find Upper Case letter in  string

 

like  

protected void CustV1_ServerValidate(object source, ServerValidateEventArgs args)
{ 

     string Char=args.Value;

      if (char.IsUpper() == true)//Error  Please Resolve me sir how to Handle i don't know because i an just beginer
    {
         CustV1.IsValid = true;
    } 

}