C# Online Compiler | .NET Fiddle

using System;

public static class Program
{
	    /// <summary>
        /// Define common patterns for substring actions
        /// </summary>
        public enum StrCut
        {
            BeforeLessStr = 0,
            BeforeInclStr = 1,
            AfterLessStr = 2,
            AfterInclStr = 4
        }
        /// <summary>
        /// Cut from front or back
        /// </summary>
        public enum StrCutLoc
        {
            First = 0,
            Last = 1
        }
        /// <summary>
        /// Extend Susbstring with ability to pass a string and choose common actions surrounding that string.
        /// </summary>
        /// <param name="s">haystack</param>
        /// <param name="arg">needle</param>
        /// <param name="l">search location</param>
        /// <param name="e">include needle</param>
        /// <returns></returns>
        /// <author>//Fri 31-May-19 12:45pm metadataconsult@gmail.com</author>
        public static string Substring(this string s, string arg, StrCutLoc l, StrCut e)
        {
            //Range checking, why do you neet a unit test
            if (string.IsNullOrEmpty(s) || string.IsNullOrEmpty(arg)) return string.Empty;
            if (arg.Length > s.Length) return string.Empty;

            int idxarg = -1; 

            if (l.Equals(StrCutLoc.First))
                idxarg = s.IndexOf(arg);
            else if (l.Equals(StrCutLoc.Last))
                idxarg = s.LastIndexOf(arg);
       
            if (idxarg == -1) return string.Empty; //is arg found in string

            bool argfits = (idxarg + arg.Length) <= s.Length; //is arg within limit of end of string
            
            if (e.Equals(StrCut.BeforeLessStr))
            {
                s = s.Substring(0, idxarg);
            }
            else if (argfits && e.Equals(StrCut.BeforeInclStr))
            {
                s = s.Substring(0, (idxarg + arg.Length));
            }
            else if (argfits && e.Equals(StrCut.AfterLessStr))
            {
                s = s.Substring(idxarg + arg.Length);
            }
            else if (e.Equals(StrCut.AfterInclStr))
            {
                s = s.Substring(idxarg);
            }
            return s;
        }
	
	public static void Main()
	{
		string text = "{\"InsertSymbolText\",\"InsertSymbol\"},";  
		string cut = ",";
	
		Console.WriteLine("text = "+ text); 
		Console.WriteLine();
		Console.WriteLine("Let's get rid of length param, like this Substring(2,2) = " + text.Substring(2,2)); 
		Console.WriteLine();
	
		Console.WriteLine("BEGIN - Most of time, I just want to get a supply a string a work around it"); 
		
		Console.WriteLine("AfterLessStr = " + text.Substring(cut, StrCutLoc.First, StrCut.AfterLessStr));
		Console.WriteLine("AfterInclStr = " + text.Substring(cut, StrCutLoc.First, StrCut.AfterInclStr));
		Console.WriteLine("BeforeInclStr = " + text.Substring(cut, StrCutLoc.Last, StrCut.BeforeInclStr));
		Console.WriteLine("BeforeLessStr = " + text.Substring(cut, StrCutLoc.Last, StrCut.BeforeLessStr));
		Console.WriteLine("END");
	}
}

 
using System;
​
public static class Program
{
        /// <summary>
        /// Define common patterns for substring actions
        /// </summary>
        public enum StrCut
        {
            BeforeLessStr = 0,
            BeforeInclStr = 1,
            AfterLessStr = 2,
            AfterInclStr = 4
        }
        /// <summary>
        /// Cut from front or back
        /// </summary>
        public enum StrCutLoc
        {
            First = 0,
            Last = 1
        }
        /// <summary>
        /// Extend Susbstring with ability to pass a string and choose common actions surrounding that string.