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# Adding FrontEnd validator
WebForms has control [validators](https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.webcontrols.basevalidator?view=netframework-4.8), you can add a validator to a [newly added control](/webmap/winforms/extend-or-modify-the-converted-application/adding-a-component.md).
Let's say you want to add a required validator for a new textbox control.
Add the required validator in the Frontend and set an unique id.
**myPage.html**
```typescript
```
Then, you have to declare the validator in the Backend file.
**myPage.designer.cs**
```csharp
[Intercepted]
protected Mobilize.Web.UI.Controls.RequiredFieldValidator rev1 { get; set; }
```
In the same file you have to initialize and set the necessary properties in the `InitializeComponent` method
```csharp
this.rev2 = new Mobilize.Web.UI.Controls.RequiredFieldValidator();
this.rev2.Name = "rev1";
this.rev2.ControlToValidate = "Textbox2";
this.rev2.ErrorMessage = "Validator Error Message";
this.Controls.Add(this.rev2);
```
The `ControlToValidate` property must be the same as the `Control.Name` you want to validate. In the previous example we have a textbox with that name.
```csharp
this.TextBox2.Name = "Textbox2";
```
After these changes the new validator is ready.
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