[Solved] C# – How do I put the Function Regex working? [closed]

Question

this is not an issue with the bit of code you showed.

This is a namespace issue at the very top of your file.

The solution should be https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/namespaces/

using System;
using System.Text.RegularExpressions;
    
public class Test
{            
    public static void Main ()
    {
        var isNumeric1 = IsNumeric("1");
        Console.WriteLine(isNumeric1);

        var isNumeric2 = IsNumeric("HelloWorld");
        Console.WriteLine(isNumeric2);

        //call IsNumeric with the value of this.txtIdGrupo.Text like this
        //var isNumeric = IsNumeric(this.txtIdGrupo.Text);
    }

    private static bool IsNumeric(string str)
    {
        string id = str;

        if (!Regex.IsMatch(id, @"^\d+$"))   
            return false;

        return true;
    }
}

See it in action:
https://dotnetfiddle.net/I7cAKs

notice the “using System.Text.RegularExpressions”

Using tools like Resharper and similar will definitely give you hints and will improve your day to day !

Accepted Answer