I know it can't be done since using var can only be done for local variables. I'm just wondering if anyone has a theory why the C# team thought this should be so. e.g. what would be wrong with this:

public class SomeClass
{
    var someString = "hello"; //not cool
    public SomeClass()
    {
        var someOtherString = "hello"; //cool
    }
}

If someString is initialised then it is obviously a string just like someOtherString. Why is there one rule for local variables and another for globals?