Merge pull request #703 from telerik/new-kb-maskededitbox-prevent-losing-focus-validation-failure-3a09183394204d78965bdde373fb8335

Added new kb article maskededitbox-prevent-losing-focus-validation-failure

Author: nade7o

knowledge-base/maskededitbox-prevent-losing-focus-validation-failure.md

@@ -0,0 +1,46 @@
+---
+title: Preventing RadMaskedEditBox from Losing Focus on Validation Failure
+description: Learn how to keep the focus on a RadMaskedEditBox for WinForms when the Email mask validation fails.
+type: how-to
+page_title: How to Keep Focus on RadMaskedEditBox with Email MaskType on Validation Failure
+slug: maskededitbox-prevent-losing-focus-validation-failure
+tags: editors, maskededitbox, winforms, validation, focus
+res_type: kb
+ticketid: 1677692
+---
+
+## Environment
+
+|Product Version|Product|Author|
+|----|----|----|
+|2025.1.211|RadMaskedEditBox for WinForms|[Dinko Krastev](https://www.telerik.com/blogs/author/dinko-krastev)|
+
+## Description
+
+In scenarios where a RadMaskedEditBox is used with an Email MaskType, it's crucial to ensure the input is valid before allowing the user to move focus away from the control. This article demonstrates how to prevent focus loss from a RadMaskedEditBox when email validation fails.
+
+## Solution
+
+To achieve this, handle the `Validating` event of the RadMaskedEditBox. Within the event handler, invoke the `Validate()` method of the `EMailMaskTextBoxProvider`, which is accessible via the `Provider` property of the `MaskedEditBoxElement`. If the validation fails, set the `Cancel` property of the `System.ComponentModel.CancelEventArgs` parameter to `true` to prevent focus change.
+
+````C#
+// Subscribe to the Validating event
+this.radMaskedEditBox1.Validating += RadMaskedEditBox1_Validating;
+
+// Validating event handler
+private void RadMaskedEditBox1_Validating(object sender, System.ComponentModel.CancelEventArgs e)
+{
+    // Perform the validation
+    bool isValid = ((EMailMaskTextBoxProvider)this.radMaskedEditBox1.MaskedEditBoxElement.Provider).Validate(this.radMaskedEditBox1.MaskedEditBoxElement.Text);
+    // If validation fails, cancel the event to prevent focus loss
+    if (!isValid)
+    {
+        e.Cancel = true;
+    }
+}
+````
+
+
+## See Also
+
+- [RadMaskedEditBox Overview](https://docs.telerik.com/devtools/winforms/controls/editors/maskededitbox/maskededitbox)