From:
http://elevenwolf.cnblogs.com/archive/2004/07/23/26969.html
1.一个应用程序只能被用户打开一次
Process mobj_pro =Process.GetCurrentProcess();
Process[] mobj_proList=Process.GetProcessesByName(mobj_pro.ProcessName);
if(mobj_proList.Length>1)
{
MessageBox.Show("当前的应用程序已打开！", "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1);
return;
} 2.一个框架窗口下只打开一个子窗口
CustomerAdd pobj_CustomerAdd;
Form pobj_CustomerAdd_Return=CheckIsExit("CustomerAdd");
if(pobj_CustomerAdd_Return==null)
{
pobj_CustomerAdd=new CustomerAdd();
OpenSheet(pobj_CustomerAdd);
}
else
{
OpenSheet((CustomerAdd)pobj_CustomerAdd_Return);
} void OpenSheet(Form pobj_form)
{
pobj_form.MdiParent=this;
pobj_form.Show();
}
/**//**//**//// <summary>
/// 判断窗口是否存在
/// </summary>
/// <param name="ps_windowName">窗口的名称</param>
/// <returns>存在返回此窗口的实例 不存在返回null</returns> Form CheckIsExit(string ps_windowName)
{
for(int i=0;i<this.MdiChildren.Length;i++)
{
if(this.MdiChildren[i].Name==ps_windowName)
{
return this.MdiChildren[i];
}
}
return null;
} 3.弹出式窗口显示渐变效果
在页面上添加一个timer控件fadeTimer,interval设为50
类的实例变量为
private m_showing=true;
在form_load中写：
Opacity = 0.0;
Activate();
Refresh();
fadeTimer.Start();
Refresh(); 在timer控件的Tick事件中写：
if (m_showing)
{
double d = 1000.0 / fadeTimer.Interval / 100.0;
if (Opacity + d >= 1.0)
{
Opacity = 1.0;
fadeTimer.Stop();
}
else
{
Opacity += d;
}
}
else
{
double d = 1000.0 / fadeTimer.Interval / 100.0;
if (Opacity - d <= 0.0)
{
Opacity = 0.0;
fadeTimer.Stop();
}
else
{
Opacity -= d;
}
} 4.在控件textbox中实现按回车键相当于tab键的作用
public class OSTextBox:TextBox
{
public OSTextBox()
{
}
bool mb_IsKeyEnter=true;
[
Category("Data"),
DefaultValue(true),
MergableProperty(false)
]
public bool IsKeyEnter
{
get
{
return mb_IsKeyEnter;
}
set
{
mb_IsKeyEnter=value;
}
}
protected override void OnKeyPress(KeyPressEventArgs e)
{
base.OnKeyPress (e);
if(mb_IsKeyEnter)
{
if (e.KeyChar == (char)Keys.Enter)
{
SendKeys.Send("{Tab}");
}
}
}
} 
