Search of Any in a Generic LIst (VB to C# conversion)

Question

I have inherited a VB application and am looking for converting some things to C# (part of migration). I have an extension method in VB that is like this:

<Extension()>
    Public Function ContainsAnyOf(Of T)(SourceList As List(Of T), ParamArray ParamList() As T) As Boolean
        If SourceList IsNot Nothing AndAlso ParamList IsNot Nothing Then
            For Each ParamItem As T In ParamList
                If SourceList.Contains(ParamItem) Then Return True
            Next
        End If
        Return False
    End Function

I have translated it to C# as follows:

public static bool ContainsAnyOf<T>(this List<T> sourceList, IEnumerable<T> parameters)
        {
            if (parameters.Count() == 0 || sourceList == null || sourceList.Count < 1)
            {
                return false;
            }
            else
            {
                foreach (var parameter in parameters)
                {
                    if (sourceList.Contains(parameter))
                        return true;
                    else
                        return false;
                }

                return false;
            }
        }

To be complete, the model is declared in a separate cs-file as follows:

public class TestModel
    {
        public int Id { get; set; }
        public string ModelValue1 { get; set; }
        public string ModelValue2 { get; set; }
        public bool ModelBool { get; set; }
    }

In a testapplication (console) I have following testcode:

var testAnyOf = false;
var testElement = new List<string>(){ "Test 2", "Testje 2" };

if (model.ContainsAnyOf(testElement))
{
    testAnyOf = true;
}

Console.WriteLine($"Does the list contains the {testElement}? Outcome = {testAnyOf}");
Console.ReadLine();

But I get a compiler error CS0411: The type arguments for method 'ListExtensions.ContainsAnyOf(List, IEnumerable)' canot be inferred from the usage ...

I know that what the Error means but I have tried few things now but still don't know how to pass the 'Parameters'.

Eventually what I need is like in the original VB application and that works like:

bool isInList = alistOfModel.ContainsAnyOf("One", "Dog", "Hat")

I think the first part with the List of type T is correct but how to pass the parameters.. Thanks!

Answer 1

That should compile if model is of type List<string>. I assume that model is of some other type.

However, I would implement this using Linq like so (likely to be much more performant):

public static bool ContainsAnyOf<T>(this IEnumerable<T> sourceList, IEnumerable<T> parameters)
{
    return sourceList.Intersect(parameters).Any();
}

You could also use params so that you can call it with an argument list of items to match:

public static bool ContainsAnyOf<T>(this IEnumerable<T> sourceList, params T[] parameters)
{
    return sourceList.Intersect(parameters).Any();
}

Using the latter, instead of writing

var testElement = new List<string>(){ "Test 2", "Testje 2" };

if (model.ContainsAnyOf(testElement))

You could write

if (model.ContainsAnyOf("Test 2", "Testje 2"))

Answer 2

If you want a direct translation of that VB code then this is it:

public bool ContainsAnyOf<T>(this List<T> SourceList, params T[] ParamList)
{
    if (SourceList != null && ParamList != null)
    {
        foreach (T ParamItem in ParamList)
        {
            if (SourceList.Contains(ParamItem))
                return true;
        }
    }
    return false;
}

If you're going to be translating VB to C# then I suggest that you download and install Instant C# from Tangible Software Solutions.

BTW, there's never any point to null-checking a parameter declared params/ParamArray as they will always have a value. They may be empty but the array will always exist.