Generic(s) question

[rliq]

Another class has a collection of ColumnBase items in it. I want my Columns to contain different Types (literally) of data. Analogous to an SQL database. The data for the column always originates from a string (one time only). But once the data is in the column, I want it to appear to be the correct Type. So far I have:

public abstract class ColumnBase
{
    protected string _value;

    public string SetValue(String value)
    {
        _value = value;
    }
}

public class Column<T> : ColumnBase
{
    public T GetValue()
    {
        return (T)_value;   // won't allow conversion to T from string
    }
}

I'm hoping to be able to do something like:

public void foo()
{
    Column<int> myIntColumn = new Column<int>;

    myIntColumn.SetValue("31");

    int myValue = myIntColumn.GetValue();
}

My Types will be int, bool, string and double.
Is there a neat solution to the problem with the GetValue() member?