Question

What should my regular expression look like if I want to validate that $/Folder1/Folder2/Folder3/File.xml always starts with $ and always ends with xml

"$/Folder1/Folder2/Folder3/File.xml"
Pass

"$/Folder1/Folder2/Folder3/File.xm"
Fail

"$/Folder1/Folder2/Folder3/File.py"
Fail

"A/Folder1/Folder2/Folder3/File.xml"
Fail

Edit… So… The right regular expression is…

"^\$.*xml$"

The the method after the implementation of the regex checker looks like…

public bool ValidateConfigPath(string config)
    {
        var match = Regex.Match(config, @"^\$.*xml$", RegexOptions.IgnoreCase);

        return match.Success;
    }

And all my unit tests pass…

[TestMethod]
    public void ValidateConfigPath_InCorrect1()
    {
        var t = new TfsWrapper();
        var isValid = t.ValidateConfigPath("$/Quantz/Main/CSS Calculator/main.py");
        Assert.IsFalse(isValid);
    }

    [TestMethod]
    public void ValidateConfigPath_InCorrect2()
    {
        var t = new TfsWrapper();
        var isValid = t.ValidateConfigPath("C:/Quantz/Main/CSS Calculator/main.xml");
        Assert.IsFalse(isValid);
    }

    [TestMethod]
    public void ValidateConfigPath_Correct()
    {
        var t = new TfsWrapper();
        var isValid = t.ValidateConfigPath("$/Quantz/Main/CSS Calculator/main.xml");
        Assert.IsTrue(isValid);
    }

Answer 1

If there’s not a strict requirement for using regular expressions, I recommend the more straight-forward approach of simply checking the starting and ending characters:

string.startswith("$") and string.endswith("xml")

With the above, the intent is absolutely clear to anyone, including people who don’t understand regular expressions.