实现如图所示登录界面，当输入正确用户名及密码时，转到主界面，否则给出错误提示。要求不同身份的登陆者拥有不同的操作权限。

源代码：

1.初始化三个string类型的变量分别用来存储用户名、密码和身份。

[csharp] view plain copyprint?

1. string yhm, mm, sf;  

string yhm, mm, sf;

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1. private void Form1_Load(object sender, EventArgs e)
2. {
3. yhm=mm="";
4. sf=radioButton1.Text;
5. }

private void Form1_Load(object sender, EventArgs e){yhm=mm="";sf=radioButton1.Text;}

2.为三个单选按钮添加CheckedChanged事件处理程序

1>学生：

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1. private void radioButton1_CheckedChanged(object sender, EventArgs e)
2. {
3. if(radioButton1.Checked)
4. {
5. sf=radioButton1.Text;
6. checkBox1.Checked = true;
7. checkBox2.Checked=checkBox3.Checked=checkBox4.Checked=checkBox5.Checked=false;
8. }
9. }

private void radioButton1_CheckedChanged(object sender, EventArgs e){if(radioButton1.Checked){sf=radioButton1.Text;checkBox1.Checked = true;checkBox2.Checked=checkBox3.Checked=checkBox4.Checked=checkBox5.Checked=false;}}

2>教师：

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1. private void radioButton2_CheckedChanged(object sender, EventArgs e)
2. {
3. if (radioButton2.Checked)
4. {
5. sf = radioButton2.Text;
6. checkBox1.Checked=checkBox2.Checked = true;
7. checkBox3.Checked = checkBox4.Checked = checkBox5.Checked = false;
8. }
9. }

 private void radioButton2_CheckedChanged(object sender, EventArgs e){if (radioButton2.Checked){sf = radioButton2.Text;checkBox1.Checked=checkBox2.Checked = true;checkBox3.Checked = checkBox4.Checked = checkBox5.Checked = false;}}

3>管理员：

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1. private void radioButton3_CheckedChanged(object sender, EventArgs e)
2. {
3. if (radioButton3.Checked)
4. {
5. sf = radioButton3.Text;
6. checkBox1.Checked = checkBox2.Checked = checkBox3.Checked = checkBox4.Checked = checkBox5.Checked = true;
7. }
8. }

private void radioButton3_CheckedChanged(object sender, EventArgs e){if (radioButton3.Checked){sf = radioButton3.Text;checkBox1.Checked = checkBox2.Checked = checkBox3.Checked = checkBox4.Checked = checkBox5.Checked = true;}}

3.为四个Button按钮添加Click事件：

1>确定：

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1. private void button1_Click(object sender, EventArgs e)
2. {
3. yhm = textBox1.Text.Trim();
4. mm = textBox2.Text.Trim();
5. if (yhm == "xs" && mm == "xs" && sf == "学生")
6. {
7. tabControl1.SelectedTab = tabPage2;
8. panel2.Visible = true;
9. button4.Enabled = button5.Enabled = button6.Enabled = button7.Enabled = false;
10. panel1.Visible = false;
11. }
12. else if (yhm == "js" && mm == "js" && sf == "教师")
13. {
14. tabControl1.SelectedTab = tabPage2;
15. panel2.Visible = true;
16. button3.Enabled=button4.Enabled = true;
17. button5.Enabled = button6.Enabled = button7.Enabled = false;
18. panel1.Visible = false;
19. }
20. else if (yhm == "gly" && mm == "gly" && sf == "管理员")
21. {
22. tabControl1.SelectedTab = tabPage2;
23. panel2.Visible = true;
24. button3.Enabled=button4.Enabled = button5.Enabled = button6.Enabled = button7.Enabled = true;
25. panel1.Visible = false;
26. }
27. else
28. MessageBox.Show("用户名或密码错误","登录失败");
29. }

 private void button1_Click(object sender, EventArgs e){yhm = textBox1.Text.Trim();mm = textBox2.Text.Trim();if (yhm == "xs" && mm == "xs" && sf == "学生"){tabControl1.SelectedTab = tabPage2;panel2.Visible = true;button4.Enabled = button5.Enabled = button6.Enabled = button7.Enabled = false;panel1.Visible = false;}else if (yhm == "js" && mm == "js" && sf == "教师"){tabControl1.SelectedTab = tabPage2;panel2.Visible = true;button3.Enabled=button4.Enabled = true;button5.Enabled = button6.Enabled = button7.Enabled = false;panel1.Visible = false;}else if (yhm == "gly" && mm == "gly" && sf == "管理员"){tabControl1.SelectedTab = tabPage2;panel2.Visible = true;button3.Enabled=button4.Enabled = button5.Enabled = button6.Enabled = button7.Enabled = true;panel1.Visible = false;}elseMessageBox.Show("用户名或密码错误","登录失败");}

2>取消：

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1. private void button2_Click(object sender, EventArgs e)
2. {
3. this.Close();
4. }

private void button2_Click(object sender, EventArgs e){this.Close();}

3>注销登录：

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1. private void button8_Click(object sender, EventArgs e)
2. {
3. panel1.Visible = true;
4. panel2.Visible = false;
5. textBox1.Text = textBox2.Text = "";
6. radioButton1.Checked = true;
7. tabControl1.SelectedTab = tabPage1;
8. }

private void button8_Click(object sender, EventArgs e){panel1.Visible = true;panel2.Visible = false;textBox1.Text = textBox2.Text = "";radioButton1.Checked = true;tabControl1.SelectedTab = tabPage1;}

4>退出系统：

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1. private void button9_Click(object sender, EventArgs e)
2. {
3. Application.Exit();
4. }

private void button9_Click(object sender, EventArgs e){Application.Exit();}    

运行结果展示图：