using System;

 using System.Collections.Generic;

 using System.Runtime.InteropServices;

 using System.Windows.Forms;

 namespace StringToImage

 {

     static class Program

     {

         [DllImport("user32.dll")]

         public static extern IntPtr FindWindow(String classname, String title);

         [DllImport("user32.dll")]

         public static extern void SetForegroundWindow(IntPtr hwnd);

         [STAThread]

         static void Main()

         {

             Application.EnableVisualStyles();

             Application.SetCompatibleTextRenderingDefault(false);

             string p = System.Diagnostics.Process.GetCurrentProcess().ProcessName;

             System.Diagnostics.Process[] processes = System.Diagnostics.Process.GetProcessesByName(p);

             if (processes.Length < )

                 Application.Run(new Form1());

             else

             {

                 //MessageBox.Show("程序已经运行!", "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

                 IntPtr ptr = FindWindow(null, "文字转换成图片");//"文字转换成图片"为对应窗体的Text值

                 if (ptr.ToString() != "")//不等于0表示找到了窗体

                     SetForegroundWindow(ptr);

                 Application.Exit();

             }

         }

     }

 }