Need regex code to replace a particular variable name in an expression by some value.

Try something like this:

using System;

using System.Text.RegularExpressions;

class Test

{

static void Main()

{

string[] variables = {"a", "aa", "b"};

string[] values = {"1", "2", "3"};

string expression = "a+aa-b";

for(int i = 0; i < 3; i++)

{

string regExp = @"(?'prev'(^|\W))" + variables[i] + @"(?'next'($|\W))";

string replacement = "${prev}" + values[i] + "${next}";

string newExp = Regex.Replace(expression, regExp, replacement);

Console.WriteLine(newExp);

}

Console.ReadKey();

}

}

The output should be:

1+aa-b

a+2-b

a+aa-3