关于c＃：Winform Collection被修改了;

Winform Collection was modified; enumeration operation may not execute

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我的代码是：

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private void studentToolStripMenuItem_Click(object sender, EventArgs e)
{

foreach (Form frm in Application.OpenForms)
{
if (frm.Text =="student")
{
frm.Activate();
}
else
{
studetn obj = new studetn();
obj.MdiParent = this;
obj.Dock = DockStyle.Fill;
obj.Show();
}
}
}

相关讨论

show()命令修改正在枚举的application.openforms集合。这是不允许的。您应该在foreach循环之外创建和显示新表单：

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private void studentToolStripMenuItem_Click(object sender, EventArgs e)
{
// Find the student form
Form frmStudent = null;
foreach (Form frm in Application.OpenForms)
{
if (frm.Text =="student")
{
frmStudent = frm;
break;
}
}
// if found - activate, if not found - create
if(frmStudent!=null)
{
frmStudent.Activate();
}
else
{
studetn obj = new studetn();
obj.MdiParent = this;
obj.Dock = DockStyle.Fill;
obj.Show();
}
}