How to Add Spaces before Capital letter in a string using C#?

Try using this below Linq code(without using regex) to add space before capital letters

var YourString= "NoEffect";

//get output as "No Effect"
@string.Concat(YourString.Select(x => Char.IsUpper(x) ? " " + x : x.ToString())).TrimStart(' ');

This should work.

Here is the simple program to add space before capital letters using regex in C#

using System;
using System.Text.RegularExpressions;
					
public class Program
{
	public static void Main()
	{
		var oldvalue= "ThisIsTest";
		var newValue = Regex.Replace(oldvalue, "([a-z])([A-Z])", "$1 $2");
		Console.WriteLine(newValue);
	}
}

Output:

This Is Test

You can check the fiddle here https://dotnetfiddle.net/4V0v70 but above Linq Solutions looks easy and simple to me.

If you want to create Extension method to add space before capital 

public static class Extensions
{
    public static string SpaceBeforeCapital( this string Input )
    {
        return new string(Input.SelectMany((c, i) => i > 0 && char.IsUpper(c) ? new[] { ' ', c } : new[] { c }).ToArray());
    }
}

Now you can use it like MyCasedString.SpaceBeforeCapital() this.