Question

I want to replace a charecter in a string with a string in c#.
I have tried the following,

Here in the following program, i want replace set of charecters between charecters ‘:’ and first occurance of ‘-‘ with some others charecters.

I could able to extract the set of charecters between ‘:’ and first occurance of ‘-‘.

Can any one say how to insert these back in the source string.

        string source= "tcm:7-426-8";
        string target= "tcm:10-15-2";
        int fistunderscore = target.IndexOf("-");
        string temp = target.Substring(4, fistunderscore-4);
        Response.Write("<BR>"+"temp1:" +   temp + "<BR>");

Examples:

        source: "tcm:7-426-8" or "tcm:100-426-8" or "tcm:10-426-8"

        Target: "tcm:10-15-2" or "tcm:5-15-2" or "tcm:100-15-2"

        output: "tcm:10-426-8" or "tcm:5-426-8" or "tcm:100-426-8"

In a nutshell, I want to replace the set of charectes between ‘:’ and ‘-‘(firstoccurance) and the charecters extracetd from the same sort of string.

Can any help how it can be done.

Thank you.

Answer 1

Try a regex solution – first this method, takes the source and target strings, and performs a regex replace on the first, targetting the first numbers after the ‘tcm’, which must be anchored to the start of the string. In the MatchEvaluator it executes the same regex again, but on the target string.

static Regex rx = new Regex("(?<=^tcm:)[0-9]+", RegexOptions.Compiled);

public string ReplaceOneWith(string source, string target)
{
    return rx.Replace(source, new MatchEvaluator((Match m) =>
    {
        var targetMatch = rx.Match(target);
        if (targetMatch.Success)
            return targetMatch.Value;
        return m.Value; //don't replace if no match
    }));
}

Note that no replacement is performed if the regex doesn’t return a match on the target string.

Now run this test (probably need to copy the above into the test class):

[TestMethod]
public void SO9973554()
{
    Assert.AreEqual("tcm:10-426-8", ReplaceOneWith("tcm:7-426-8", "tcm:10-15-2"));
    Assert.AreEqual("tcm:5-426-8", ReplaceOneWith("tcm:100-426-8", "tcm:5-15-2"));
    Assert.AreEqual("tcm:100-426-8", ReplaceOneWith("tcm:10-426-8", "tcm:100-15-2"));
}