CODEWITHSUNDEEP
c#asp.netvaranonymous-types
Imad
Imad

Reputation: 7490

var not getting implicit value

I just came across the code below:

public void ListControls(ControlCollection controls, List<Control> controlsFound)
{
    foreach (var control in controls)
    {
        if (control is IAttributeAccessor)
        {
            controlsFound.Add(control); //Error (Invalid argument to Add method)
            ListControls(control.Controls, controlsFound);
        }
    }
}

It gives an error as above:

If I change var in foreach to Control then it works. The reason is that the Add method was expecting Control as parameter. But I think var should have been implicitly replaced by Control, right?

Upvotes: 0

Views: 78

Answers (2)

Tsef
Tsef

Reputation: 1038

Using LINQ will work:

public void ListControls(ControlCollection controls, List<Control> controlsFound)
    {
        foreach (var control in controls.OfType<Control>())
        {
            if (control is IAttributeAccessor)
            {
                controlsFound.Add(control); //Error (Invalid argument to Add method)
                ListControls(control.Controls, controlsFound);
            }
        }
    }

Upvotes: 1

Jamiec
Jamiec

Reputation: 136174

No, it doesnt because ControlCollection only implements the non-generic IEnumerable not the generic IEnumerable<Control> so when you enumerate it without providing the type, you get object

Upvotes: 4

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