Try something like this:
using System;
public class Program
{
public static void Main()
{
Console.WriteLine(Compute());
}
private static string Compute(){
string message = string.Empty;
bool isValid = true;
double result = 0;
string sampleText = "2+5+1+6+3+2+1";
string delimtedValue = "+";
if(sampleText.Contains(delimtedValue)){
string[] numbers = sampleText.Split(delimtedValue.ToCharArray());
double val;
foreach(string num in numbers)
{
if (!double.TryParse(num, out val))
{
message ="Unable to compute. String has invalid numeric values";
isValid = false;
break;
}
result = result + val;
}
}
if(!isValid)
return message;
else
return string.Format("The total sum is: {0}", result);
}
}