How Do I Manually Trigger a Paint Event in C#?

Manually trigger draw events

When drawing text on a panel, it needs to be redrawn to remove it. This article will guide you through the process of manually triggering draw events.

Methods to trigger drawing events

In your form or control method, you have three options to choose from:

• this.Invalidate();

Request message loop system to delay redrawing.

• this.Update();

Force redrawing of invalid areas.

• this.Refresh();

Combine the functions of Invalidate() and Update().

Usage suggestions

It is generally recommended to use Invalidate() for deferred redraws as the system will effectively group it with other screen updates. If an urgent redraw is required, use Refresh(), but be aware that multiple redraws may occur due to cascading failures.

Windows handles screen updates by waiting for the message queue to clear and then processing the invalid area. This is efficient because changes usually trigger subsequent updates.

Special cases of Update()

Update() is mainly used in scenarios where property changes (for example, label1.Text) occur in a for loop that blocks the message loop. If this problem recurs, consider using a separate thread.

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