Question

I have the following code:

Tuple<string, string, Type, ParameterInfo[]> method = (Tuple<string, string, Type, ParameterInfo[]>)(comboBox1.SelectedItem);
if (comboBox2.SelectedIndex - 1 >= 0)
{
    if (method.Item4[comboBox2.SelectedIndex - 1].ParameterType.BaseType == typeof(Enum))
    {
        foreach (object type in Enum.GetValues(method.Item4[comboBox2.SelectedIndex - 1].ParameterType))
        {
            Console.WriteLine(type);
        }
        MessageBox.Show("This looks like an auto-generated type; you shouldn't set it to anything.", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning, MessageBoxDefaultButton.Button1);
    }
    else if (Nullable.GetUnderlyingType(method.Item4[comboBox2.SelectedIndex - 1].ParameterType) != null)
    {
        if (Nullable.GetUnderlyingType(method.Item4[comboBox2.SelectedIndex - 1].ParameterType).BaseType == typeof(Enum))
        {
            MessageBox.Show("This looks like an auto-generated type; you shouldn't set it to anything.", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning, MessageBoxDefaultButton.Button1);
        }
    }
}

On the else if statement, I noticed that it always returns null, even though the object at method.Item4[0] in my case is always a Nullable type when the comboBox2.SelectedIndex is 1, so why is it returning null? Seriously, I put a break-point there, and in Item4, I see the object at index 0 as:

[0] = {System.Nullable`1[CarConditionEnum]& carCondition}

…and at index 1 as:

[1] = {Boolean& carConditionSpecified}

Answer 1

The problem is the parameter is a by reference type i.e. it is declared as ref CarConditionEnum? paramName.

You need to get the element type of the parameter, and then use Nullable.GetUnderlyingType:

Type paramType = method.Item4[comboBox2.SelectedIndex - 1].ParameterType;
if(paramType.HasElementType)
{
    paramType = paramType.GetElementType();
}

if(Nullable.GetUnderlyingType(paramType) != null)
{
}