Question

I am creating an application which will send the input string to mobile device. Some devices have problems with encoding special characters so I would like to create a filter which doesn’t allow the user on PC to enter special characters.

The application is written in C# (.NET 3.5) and I would like to attach a method to key press event. The pseudocode is the following:

private void checkTextBoxContent(TextBox txtEntry)
{
    if(txtEntry.Text contains non-ASCII sign)
    {
        show messageBox;
        remove the last entered character;
    }
}

Does anyone know if there is any existing method that detects ASCII/non-ASCII sign so that could be used in condition

txtEntry.Text contains non-ASCII sign?

Thank you!

Answer 1

Well you can do:

public static bool IsAllAscii(string text)
{
    return text.All(c => c >= ' ' && c <= '~');
}

I’m not sure you would really want to just remove the last character entered though – consider cutting and pasting a whole non-ascii string…