Validate File Name Number or String in C#.net

  private void   createfirstFile(string inputPath)
        {
            #region Check Directory Exists 
            if (Directory.Exists(inputPath))
            {
                cntstringName = 0;
                string[] files = Directory.GetFiles(inputPath);
                foreach (string file in files)
                {
                    string name = Path.GetFileName(file);
                    string[] str = name.Split('.');

                    foreach (char ch in str[0])
                    {
                        bool chkAlphaNum = Char.IsLetter(ch);
                         if (chkAlphaNum)
                        {
                            chk = true;
                         }
                        else
                        {
                            chk = false;
                        }
                       
                 }
                    cntstringName = cntstringName + 1;
               }
                if (chk)
                {
                    MessageBox.Show("No of string File Names:" + " " + cntstringName);
                }
                else
                {
                    MessageBox.Show("No of Numberic File Names:" + " " + cntstringName);
                }
            }
            else
            {
                MessageBox.Show("Please create a Directory and files ");
            }

  createfirstFile("Folder Path);