Is DataTable passed by reference? [duplicate]

Question

This might sound like a stupid question, but I just happened to stumbled upon this. I know you can use ref to pass a parameter by reference. But I have this method

    public void SaveRecordsIntoTemporaryTable(DataTable objDataTable, string userSessionID)
   {

       // The objDataTable has 5 columns "Id", "Name", "Tag_1", "Tag_2", "Tag_3"
       // Now in here I remove "Tag_1", "Tag_2", and "Tag_3"
       objDataTable.Columns.Remove("Tag_1");
       objDataTable.Columns.Remove("Tag_2");
       objDataTable.Columns.Remove("Tag_3");

       ...

   }

Now I have set a debug point on third line, but after I remove this column "Tag_3", and I hover my cursor over objDataTable in the parameter, the DataTable it shows also has the columns removed? So, is it getting passed by reference?

UPDATE

Okay, if it is getting passed by reference, what difference would it make if I use ref?

Answer 1

So, is it getting passed by reference?

Its address is passed by value. Since DataTable is a class (a reference type), Its address gets passed by value and hence you see the change.

Try doing:

objDataTable = null;

If it is truly passed by reference then you will see the caller setting the DataTable to null but that doesn't happen.

See: Parameter passing in C# by Jon Skeet