如何在StepArgumentTransformation中使用REGEX查找前缀字符串

Question

I want to use StepArgumentTransformation of SpecFlow to transform all strings prefixed with "key:" to something else. I don't get around on how to use the right regular expression.

Lets say I have the following step in my feature file:

Given a user is logged in with key:testkey and has password key:testpassword and username John

Which leads to this step definition:

[Given(@"a user is logged in with (.*) and has password (.*) and username (.*)")]
public void GivenUserIsLoggedIn(string key, string password, string username)
{
    // To stuff
}

Now I want to change the key values by using step argument transformation:

[StepArgumentTransformation(@"add correct regular expression here")]
public string TransformKeys(string value)
{
    // Do transformation
    return result;
}

I only want values prefixed with "key:" to enter the transformation method. How can I achieve this? I tried several stuff like

[StepArgumentTransformation(@"key:.*")
[StepArgumentTransformation(@"(key:.*)")
[StepArgumentTransformation(@"key:\w+")

But i either get error "parameter count mismatch" or the transformation method isn't entered at all.

Answer 1

Note: I am using specflow3 as version

Scenario: stackoverflow usecase
    Given a user is logged in with key:testkey and has password key:testpassword and username John

In step definition:

[Given(@"a user is logged in with (key:.*) and has password (key:.*) and username John")]
        public void GivenAUserIsLoggedInWithKeyTestkeyAndHasPasswordKeyTestpasswordAndUsernameJohn(string username, string password)
        {
            var user = username;
            var pass = password;

            Console.Write("username: {0} and password: {1} ", user, pass );
        }


[StepArgumentTransformation(@"key:(.*)")]
        public string ValueForKey(string value)
        {
            return value;
        }

Please accept the answer if working for you. What is the specflow version in your case?