Question

I’ve got 2 LINQ-to-SQL lists and I merge them into 1 list using:

var mergedList = List1.Union(List2);

I assume that the Union command will eliminate all dupes in the list. Is that right? Anyway, I’m trying to write the contents of the merged list into a csv file. I’m getting errors when I try to call the list in:

WriteToCSVFile cf = new WriteToCSVFile(mergedList);

and this is how I constructed my class:

public WriteToCSVFile(IEnumerable<T> mergedList)

What am I doing wrong here?

Btw, this are the errors I’m getting:

The type arguments for method 'WriteToCSVFile.WriteToCSVFile(System.Collections.Generic.IEnumerable<T>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
The type or namespace name 'T' could not be found (are you missing a using directive or an assembly reference?) 

If you need more info, please let me know. And thanks in advance.

Answer 1

You need to make your class generic

public class WriteToCSVFile<T>
{
    public WriteToCSVFile(IEnumerable<T> mergedList)
    {

    }

    ...
}

and when calling it specify the generic argument type because generic types cannot be inferred from constructors:

var cf = new WriteToCSVFile<TheTypeOfElementsInYourList>(mergedList);

Type inference works only with methods, so you could write an extension method:

public static class CsvExtensions
{
    public static void WriteToCSVFile<T>(this IEnumerable<T> list)
    {
        ...
    }
}

and then:

mergedList.WriteToCSVFile();

Oh, and I sincerely hope that you are not rolling your own CSV parser, do you?