如何用C#写一个简单的Login窗口

发布时间:2009年06月04日      浏览次数:418 次
看到网上经常会问如何进行窗口跳转,大多数的问题都是牵扯到Login窗口。其实,在Visual Studio 6以来,比较正确的做法,是判断Login窗口的返回值,然后决定是否打开主窗体,那么在C#中也是一样的。

具体做法如下:
首先,创建Login窗口,然后添加相应的输入框和按钮,设置窗口的AcceptButton为窗体的确认按钮,而CancelButton为窗体的取消按钮。例如:
this.AcceptButton = this.btnOK;
this.CancelButton = this.btnCancel;

定义确定按钮以及取消按钮事件,如下:
private void btnOK_Click(object sender, System.EventArgs e)
{
// Here is to use fixed username and password
// You can check username and password from DB
if( txtUserName.Text == "Admin" && txtPassword.Text == "nopassword" )
{
// Save login user info
uiLogin.UserName = txtUserName.Text;
uiLogin.Password = txtPassword.Text;

this.DialogResult = DialogResult.OK;
}
else
{
nLoginCount++;
if( nLoginCount == MAX_LOGIN_COUNT )
this.DialogResult = DialogResult.Cancel;
else
{
MessageBox.Show( "Invalid user name and password!" );
txtUserName.Focus();
}
}
}

private void btnCancel_Click(object sender, System.EventArgs e)
{
this.DialogResult = DialogResult.Cancel;
}

然后,在Login窗体的Closing事件中,要进行处理,如下:
private void frmLogin_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
if( this.DialogResult != DialogResult.Cancel &&
this.DialogResult != DialogResult.OK )
e.Cancel = true;
}

除此外,Login窗体一些辅助代码如下:
private int nLoginCount = 0;
private const int MAX_LOGIN_COUNT = 3;

private UserInfo uiLogin;
public frmLogin( ref UserInfo ui )
{
//
// Required for Windows Form Designer support
//
InitializeComponent();

// Set login info to class member
uiLogin = ui;
}

调用的时候,要修改程序的Main函数,如下:
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
UserInfo ui = new UserInfo();
frmLogin myLogin = new frmLogin( ref ui );
if( myLogin.ShowDialog() == DialogResult.OK )
{
//Open your main form here
MessageBox.Show( "Logged in successfully!" );
}
else
{
MessageBox.Show( "Failed to logged in!" );
}
}

而附加的UserInfo类如下:
/// <summary>
/// User info class
/// </summary>
public class UserInfo
{
private string strUserName;
private string strPassword;
public string UserName
{
get{ return strUserName;}
set{ strUserName = value; }
}
public string Password
{
get{ return strPassword;}
set{ strPassword = value;}
}
public UserInfo()
{
strUserName = "";
strPassword = "";
}
}
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