C#: How to Delete the matching substring between 2 strings?

Question

If I have two strings .. say

string1="Hello Dear c'Lint"

and

string2="Dear"

.. I want to Compare the strings first and delete the matching substring ..
the result of the above string pairs is:

"Hello  c'Lint"

(i.e, two spaces between "Hello" and "c'Lint")

for simplicity, we'll assume that string2 will be the sub-set of string1 .. (i mean string1 will contain string2)..

Answer 1

What about

string result = string1.Replace(string2,"");

EDIT: I saw your updated question too late :)
An alternative solution to replace only the first occurrence using Regex.Replace, just for curiosity:

string s1 = "Hello dear Alice and dear Bob.";
string s2 = "dear";
bool first = true;
string s3 = Regex.Replace(s1, s2, (m) => {
    if (first) {
        first = false;
        return "";
    }
    return s2;
});

Answer 2

Do this only:

string string1 = textBox1.Text;
string string2 = textBox2.Text;

string string1_part1=string1.Substring(0, string1.IndexOf(string2));
string string1_part2=string1.Substring(
    string1.IndexOf(string2)+string2.Length, string1.Length - (string1.IndexOf(string2)+string2.Length));

string1 = string1_part1 + string1_part2;

Hope it helps. It will remove only first occurance.