Process.WaitForInputIdle Method (Int32)


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Causes the Process component to wait the specified number of milliseconds for the associated process to enter an idle state. This overload applies only to processes with a user interface and, therefore, a message loop.

Namespace:   System.Diagnostics
Assembly:  System (in System.dll)

public bool WaitForInputIdle(
	int milliseconds


Type: System.Int32

A value of 1 to MaxValue that specifies the amount of time, in milliseconds, to wait for the associated process to become idle. A value of 0 specifies an immediate return, and a value of -1 specifies an infinite wait.

Return Value

Type: System.Boolean

true if the associated process has reached an idle state; otherwise, false.

Exception Condition

The process does not have a graphical interface.


An unknown error occurred. The process failed to enter an idle state.


The process has already exited.


No process is associated with this Process object.

Use WaitForInputIdle(Int32) to force the processing of your application to wait until the message loop has returned to the idle state. When a process with a user interface is executing, its message loop executes every time a Windows message is sent to the process by the operating system. The process then returns to the message loop. A process is said to be in an idle state when it is waiting for messages inside of a message loop. This state is useful, for example, when your application needs to wait for a starting process to finish creating its main window before the application communicates with that window.

If a process does not have a message loop, WaitForInputIdle(Int32) throws an InvalidOperationException.

The WaitForInputIdle(Int32) overload instructs the Process component to wait a finite amount of time for the process to become idle in the message loop. If the associated process has not become idle by the end of the interval because the loop is still processing messages, false is returned to the calling procedure.

For more information about handling events, see Handling and Raising Events.


for full trust for the immediate caller. This member cannot be used by partially trusted code.

.NET Framework
Available since 1.1
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