# Validation

InputPanel provides validation feature to alert invalid inputs. Award-Winning Suite of Controls for .NET Development. Read the documentation to know more.

## Content



InputPanel displays a default red frame automatically around an input component whenever user provides an invalid input. Appearance of the default red frame can be customized by using the **ErrorFrameColor** and **ErrorFrameThickness** properties of the <span data-popup-content="\u003cp\u003eThis class is available in \u003ca href=\u0022/componentone/docs/win/online-inputpanel/\u0022\u003e.NET\u003c/a\u003e and \u003ca href=\u0022/componentone/docs/win/online-inputpanel/\u0022\u003e.NET Framework\u003c/a\u003e.\u003c/p\u003e" data-popup-title="C1InputPanel" data-popup-theme="ui-tooltip-green qtip-green">C1InputPanel</span> class. For more information, see [Customize Error Frame](/componentone/docs/win/online-inputpanel/appearanceandstyle).

![Validation](https://cdn.mescius.io/document-site-files/images/4e65bab9-2efa-46a9-bc67-a45339527116/images/validation.png)

In addition to the visual alert, you can also provide a text alert for invalid input. InputPanel has an **ErrorText** property that displays the specified string as a popup error when you move the mouse over the input component.

**csharp**

```csharp
mtb.Mask = "(000)000-0000";
mtb.ErrorText = "<table><tr><td><b>Invalid value</b></td></tr>" +
       "<tr><td style = 'margin:1 12'>Enter a valid phone number with area code.</td></tr></table>";
```

**vbnet**

```vbnet
mtb.Mask = "(000)000-0000"
mtb.ErrorText = "<table><tr><td><b>Invalid value</b></td></tr>" & 
"<tr><td style = 'margin:1 12'>Enter a valid phone number with area code.</td></tr></table>"                        
```

## See Also

[Appearance and Style](/componentone/docs/win/online-inputpanel/appearanceandstyle)

[Keyboard Navigation](/componentone/docs/win/online-inputpanel/keyboardnavigation)