测试语法着色不成功

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace takeexecl
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (this.openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = openFileDialog1.FileName;
            }
            
        }
    }
}