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Form.TopLevel Property

Gets or sets a value indicating whether to display the form as a top-level window.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

[BrowsableAttribute(false)]
public bool TopLevel { get; set; }

Property Value

Type: System.Boolean
true to display the form as a top-level window; otherwise, false. The default is true.

ExceptionCondition
Exception

A Multiple-document interface (MDI) parent form must be a top-level window.

A top-level form is a window that has no parent form, or whose parent form is the desktop window. Top-level windows are typically used as the main form in an application.

The following code example use the Modal property to determine if a form is displayed as a modal form. If it is not the FormBorderStyle and TopLevel properties are changed to make the form non-top-level form with a tool window border.

		private void ShowMyNonModalForm()
		{
			Form myForm = new Form();
			myForm.Text = "My Form";
			myForm.SetBounds(10,10,200,200);

			myForm.Show();
			// Determine if the form is modal. 
			if(myForm.Modal == false)
			{
				// Change borderstyle and make it not a top level window.
				myForm.FormBorderStyle = FormBorderStyle.FixedToolWindow;
				myForm.TopLevel = false;
			}
		}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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