SpecFlow doesn't support optional parameters in the step
definition methods. You have to write two methods, but you can
simply call one from the other.
[Given(@"Add two numbers (.*) (.*) (.*)")]
public void Testtheconditionwith(string a, string b, string c)
{
}
[Given(@"Add two numbers (.*) (.*)")]
public void Testtheconditionwith(string a, string b)
{
Testtheconditionwith(a,b,null)
}