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Question

I want to pass a generic Lookup<type1, type2> to an object. In this object I want to iterate over the generic lookup while accessing specific properties. How Can I do this?

A different approach would also be ok for me. I have Enumerable<type> which I have to group by any property (thats why I've choosen Lookup ). In the target Object I have to iterate group-wise over this collection and then iterate over each group, picking specific properties of type .

class Record
{
    public DateTime RecordDate {get; set;}
    public string Info1 {get; set;}
    public string Info2 {get; set;}
}

class TargetObject<type1, type2>
{
    public Lookup<type1, type2> myLookup;
    public TargetObject(Lookup<type1, type2> lookup)
    {
        myLookup = lookup;
    }

    public void TestFunc()
    {
        foreach(var item in myLookup)
        {
            var x = item.Key;
            foreach(var subItem in item)
            {
                var y = subItem. //here i like to acces type2-specific properties like Record.Info2 in a generic way
            }
        }
    }
}

List<Record> records = new List<Record>();
Lookup<DateTime, Record> lookup = records.ToLookup(r => r.RecordDate);

var target = new TargetObject(lookup);

Answer 1

//here i like to acces type2-specific properties like Record.Info2 in a generic way

The problem is, if you're truly generic, you don't know what those properties are. For that matter, neither do we. What do you want to do this data? It seems like you won't know that answer up front.

But there's good news... that makes this the perfect use case for a delegate!

public void TestFunc(Action<type1, type2> doSomething)
{
    foreach(var item in myLookup)
    {
        var x = item.Key;
        foreach(var subItem in item)
        {
            doSomething(x, subItem);
        }
    }
}

And now you'd call it with a lambda, like this:

var target = new TargetObject(lookup);
target.TestFunc((x, y) => {
    // x is the key
    // y is the subitem
    // Whatever code you put here will run once for every subitem.
    // And you will be able to use properties and methods of y.
    // As a bonus, you also have access to variables in outer scope via closures.
});