关于this指针的 error....求解答


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 Picturer_1
{
    public partial class Login : Form
    {
        public Login()
        {
            //windows窗体设计器支持所必需的
            InitializeComponent();
            //向组合框添加3个选项
            comboname.Items.Add("王菲");
            comboname.Items.Add("张强");
            comboname.Items.Add("李铁");            //将组合框的选定项设置为第一项
            comboname.SelectedIndex = 0;
        }        private void comboname_SelectedIndexChanged(object sender, EventArgs e)
        {
            txtpassw.Focus();
            switch (comboname.Text)
            {
                case "王菲":
                    {
                        txttitle.Text = "总经理";
                        txtlevel.Text = "一级";
                        picB.Image = Image.FromFile(@"C:\Users\YE\Documents\Visual Studio 2010\Projects\Picturer_1\bmp\a.jpg");
                        txtit.Text = "公司总经理，2005年1月加入本公司";
                        break;
                    }
                case "张强":
                    {
                        txttitle.Text = "副总经理";
                        txtlevel.Text = "二级";
                        picB.Image = Image.FromFile(@"C:\Users\YE\Documents\Visual Studio 2010\Projects\Picturer_1\bmp\b.jpg");
                        txtit.Text = "副总经理，2004年3月加入本公司";
                        break;
                    }
                case "李铁":
                    {
                        txttitle.Text = "经理";
                        txtlevel.Text = "三级";
                        picB.Image = Image.FromFile(@"C:\Users\YE\Documents\Visual Studio 2010\Projects\Picturer_1\bmp\c.jpg");
                        txtit.Text = "经理，2004年8月加入本公司";
                        break;
                    }
            }
        }        private void btnOk_Click(object sender, EventArgs e)
        {
            txtpassw.Focus();
            switch (comboname.Text)
            {
                case "王菲":
                    {
                        if (txtpassw.Text == "123456")
                        {
                            MessageBox.Show("输入密码正确");
                            this.Close;
                            break;
                        }
                        else
                        {
                            MessageBox.Show("你输入的密码不正确，请重新输入密码");
                            txtpassw.SelectionStart = 0;
                            txtpassw.SelectionLength = txtpassw.Text.Length;
                            break;
                        }
                    }
                case "张强":
                    {
                        if (txtpassw.Text == "234567")
                        {
                            MessageBox.Show("输入密码正确");
                            this.Close;
                            break;
                        }
                        else
                        {
                            MessageBox.Show("你输入的密码不正确，请重新输入密码");
                            txtpassw.SelectionStart = 0;
                            txtpassw.SelectionLength = txtpassw.Text.Length;
                            break;
                        }
                    }
                case "李铁":
                    {
                        if (txtpassw.Text == "345678")
                        {
                            MessageBox.Show("输入密码正确");
                            this.Close;
                            break;
                        }
                        else
                        {
                            MessageBox.Show("你输入的密码不正确，请重新输入密码");
                            txtpassw.SelectionStart = 0;
                            txtpassw.SelectionLength = txtpassw.Text.Length;
                            break;
                        }
                    }
            }
        }
    }
}c:\users\ye\documents\visual studio 2010\Projects\Picturer_1\Form1.cs(69,29): 错误 CS0201: 只有 assignment、call、increment、decrement 和 new 对象表达式可用作语句
c:\users\ye\documents\visual studio 2010\Projects\Picturer_1\Form1.cs(85,29): 错误 CS0201: 只有 assignment、call、increment、decrement 和 new 对象表达式可用作语句
c:\users\ye\documents\visual studio 2010\Projects\Picturer_1\Form1.cs(101,29): 错误 CS0201: 只有 assignment、call、increment、decrement 和 new 对象表达式可用作语句报错语句
this.Close;请问是this指针超出了权限吗？？求指导