alface alface - 1 month ago 8
C# Question

the namespace prefix "utilities" is not defined

I am fairly new to WPFs... I was trying to bind a validation to a text box in WPF.

Here is my text box in the xaml:

<TextBox>
<TextBox.Text>
<Binding Source="{x:Static r:Settings.Default}" Path="ServerIP" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<utilities:PingValidationRule />
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>


Here is my validation class:

public class PingValidationRule : ValidationRule
{
public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
{
...
if (ipCorrect) return new ValidationResult(true, null);
else return new ValidationResult(false, "It's not an IP");
}
}


With this I have the following error:


Error The namespace prefix "utilities" is not defined.


Anyone knows why?

Answer

It is not defined because you did not define it. Look at the top of your XAML file, all the stuff like xmlns:foobar="clr-namespace:Foo.Bar". You need to define it there.

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