Question

I’m writing some examples to help me use Func<> and Lambda as I need to unravel the previous developers code on the project I am on and he uses techniques that I am not familiar with.

So I’ve written a few examples of increasing complexity from a Simple LINQ query to passing the LINQ as a FUNC to a method. That all seems OK.

Then I switched from LINQ to Lambda. Simple works OK but I can’t figure out how to pass the Lambda as (in?) a Func<>.

My code is below. I’ve marked the bit I’m stuck on as WHAT_GOES_HERE

private void some method()
{
   Dictionary<int,string> dic = new Dictionary<int,string>();

   //Set the data into the dictionary
   dic.Add(1, "Mathew");
   dic.Add(2, "Mark");
   dic.Add(3, "Luke");
   dic.Add(4, "John");
   dic.Add(5, "John");

   #region Simple LINQ as Lambda

   string searchName = "John";
   var match4 = dic.Where(entry => entry.Value == searchName).Select(entry => entry.Key);

   //Get the data out of the return from the query
   foreach (int result in match4)
   {
       int keyValue = result;
   }

   #endregion


   #region Passing the Simple LINQ as Lambda as a Func<>

   //uses the above Lambda - This works although the name used is the value of searchName
   IEnumerable<int> match5 = RunTheMethod(deligateName => match4, "John");

   //I want to have an inline Lambda as the first parameter
   IEnumerable<int> match6 = RunTheMethod(WHAT_GOES_HERE?, "John");

   foreach (int result in match6)
   {
      int keyValue = result;
   }

   #endregion
}


   public IEnumerable<int> RunTheMethod(Func<string, IEnumerable<int>> myMethodName, string name)
   {
      IEnumerable<int> i = myMethodName(name);
      return i;
   }

Any thoughts?
Richard

Answer 1

I think you want:

 RunTheMethod(name => dic.Where(entry => entry.Value == name)
                         .Select(entry => entry.Key),
              "John");

but it’s not entirely clear…