Using type object as returning type - bad practice?

Question

I have a method

    private object SetGrid(IGrid grid)
    {
        grid.PagerHelper.SetPage(1, 10);
        grid.SortHelper.SetSort(SortOperator.Ascending);
        grid.PagerHelper.RecordsPerPage = 10;

        return grid;
    }

which returns an object of type object.

Then I cast the object back to the previous type.

    var projectModel = new ProjectModel();

    projektyModel = (ProjectModel)SetGrid(projectModel);

The gain of this is, the method SetGrid can be reused across the app.

Is this a common practice or should I avoid doing this ?

Answer 1

You could use a generic method instead, and constrain the type argument to your IGrid interface:

private T SetGrid<T>(T grid) where T : IGrid
{
    grid.PagerHelper.SetPage(1, 10);
    grid.SortHelper.SetSort(SortOperator.Ascending);
    grid.PagerHelper.RecordsPerPage = 10;

    return grid;
}

You should still be able to call the method in exactly the same way, just without the cast. Type inferencing should be capable of automagically figuring out the required generic type argument for you:

var projectModel = new ProjectModel();
projektyModel = SetGrid(projectModel);

EDIT...

As other answers have mentioned, if your IGrid objects are reference types then you don't actually need to return anything at all from your method. If you pass a reference type then your method will update the original object, not a copy of it:

var projectModel = new ProjectModel();  // assume that ProjectModel is a ref type
projektyModel = SetGrid(projectModel);
bool sameObject = object.ReferenceEquals(projectModel, projektyModel);  // true

Answer 2

Since you are passing in an object of a class that implements IGrid you could just as well change the return type to IGrid.

Also, since it's a reference type you don't even need to return the grid again. You could just as well use this:

var projectModel = new ProjectModel();
SetGrid(projectModel);