Regular Expressions Cookbook

3.14. Replace All Matches

Problem

You want to replace all matches of the regular expression ‹before› with the replacement text «after».

Solution

C#

You can use the static call when you process only a small number of strings with the same regular expression:

string resultString = Regex.Replace(subjectString, "before", "after");

If the regex is provided by the end user, you should use the static call with full exception handling:

string resultString = null;
try {
    resultString = Regex.Replace(subjectString, "before", "after");
} catch (ArgumentNullException ex) {
    // Cannot pass null as the regular expression, subject string,
    // or replacement text
} catch (ArgumentException ex) {
    // Syntax error in the regular expression
}

Construct a Regex object if you want to use the same regular expression with a large number of strings:

Regex regexObj = new Regex("before");
string resultString = regexObj.Replace(subjectString, "after");

If the regex is provided by the end user, you should use the Regex object with full exception handling:

string resultString = null;
try {
    Regex regexObj = new Regex("before");
    try {
        resultString = regexObj.Replace(subjectString, "after");
    } catch (ArgumentNullException ex) {
        // Cannot pass null as the subject string or replacement text
    }
} catch (ArgumentException ex) {
    // Syntax error in the regular expression
}

VB.NET

You can use the static call when you process only a small number of strings with the same regular expression:

Dim ResultString = Regex.Replace(SubjectString, ...