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Use regular expressions to replace text in the lines in a string in C#
The program creates a Regex object, passing its constructor a regular expression pattern that will identify text to replace. It calls the object's Replace method, passing it the replacement pattern.
private void btnGo_Click(object sender, EventArgs e)The trick in this example lies in the search and replacement patterns. In this example, the search pattern is (?m)^([^,]*), ([^\r]*)\r?$. The pieces of this expression have the following meanings: Part Meaningt
{
try
{
Regex reg_exp = new Regex(txtPattern.Text);
lblResult.Text = reg_exp.Replace(
txtInput.Text,
txtReplacementPattern.Text);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
| (?m) | This is an option directive that indicates a multiline string. This makes the ^ and $ characters match the beginning and end of a line rather than the beginning and end of the string. |
| ^ | Match the beginning of a line. |
| ([^,]*) | Match any character other than comma any number of times. This part is enclosed in parentheses so it forms the first match group. |
| , | (A comma followed by a space.) Match a comma followed by a space. |
| ({^\r]*) | Match any character except carriage return any number of times. This part is enclosed in parentheses so it forms the second match group. (In C# the carriage return isn't part of the end of the line.) |
| [\r]? | Match a carriage return zero or one times. |
| $ | Match the end of the line. |
Archer, AnnAnd converts it into this:
Baker, Bob
Carter, Cindy
Deevers, Dan
Ann Archer
Bob Baker
Cindy Carter
Dan Deevers
Posted by Rod Stephens at 10/11/2010 6:06 AM 
Categories: regular expressions
Tags: parse example program string parsing strings patterns regular expressions C# example C# programming Windows Forms programming parsing replace
Categories: regular expressions
Tags: parse example program string parsing strings patterns regular expressions C# example C# programming Windows Forms programming parsing replace
Rod,
First - Thank you for the excellent site with such interesting and useful examples!
Second - After building this example, I was not able to produce the same results that you describe in the post.
The last name (Deevers, Dan) is not followed by a carriage return so it does not match. I was able to match all four names (producing the result that you included in the post) with the following regex:
(?m)^([^,]*), ([^\r]*)(\r?)$
Anyway, thank you again for sharing your knowledge!
X
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You're absolutely correct! I didn't notice the comma in the final line of output.
I've updated the example to fix it. Thanks for pointing this out!
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