无法将类型为“ System.Reflection.ParameterInfo”的对象转换为类型为“ System.Int32”的对象

Question

I'm trying to write an extension method for objects that will dump the structure of the object to the debug output. I'm running in to a problem when the propertyInfo is indexed (GetIndexParameters().Length >0).

I've tried using the following:

object value = propInfo.GetValue(myObject, propInfo.GetIndexParameteres());

this results in the following runtime error:

• Object of type 'System.Reflection.ParameterInfo' cannot be converted to type 'System.Int32'

Anyone got any ideas? The full code for the method is below:

[System.Diagnostics.Conditional("DEBUG")]
public static void DebugObject(this object debugObject)
{
    System.Diagnostics.Debug.WriteLine("Debugging object: " + debugObject.GetType().Namespace);
    System.Diagnostics.Debug.WriteLine(String.Format("> {0}", debugObject.GetType()));
    System.Diagnostics.Debug.Indent();
    try
    {
        if (debugObject.GetType().IsArray)
        {
            object[] array = ((object[])debugObject);

            for (int index = 0; index < array.Length; index++)
            {
                System.Diagnostics.Debug.WriteLine(String.Format("- {{0}} = [{1}]", index, array[index]));
            }
            return;
        }

        object value = null;
        foreach (System.Reflection.PropertyInfo propInfo in debugObject.GetType().GetProperties())
        {
            try
            {
                if (propInfo.IsIndexed())
                {
                    System.Diagnostics.Debug.WriteLine(propInfo.ReflectedType.IsArray + " is indexed");
                    // THIS IS WHERE IT CHOKES.  As an example, try sending in something of type System.Net.Mail.MailMessage;
                    value = propInfo.GetValue(debugObject, propInfo.GetIndexParameters());
                }
                else
                {
                    value = propInfo.GetValue(debugObject, null);
                }

                if (value != null)
                {
                    System.Diagnostics.Debug.WriteLine(String.Format("> {0} = [{1}]", propInfo.Name, value));

                    if (
                            (value.GetType() != typeof(string))
                            &&
                            (value.GetType() != typeof(int))
                        )
                    {
                        value.DebugObject();
                    }
                }
            }
            catch (System.Reflection.TargetParameterCountException tpce)
            {
                System.Diagnostics.Debug.WriteLine(
                    String.Format(
                        "> Could not run GetValue for {1} (type '{0}', '{2}') because of incorrect prarmeters", 
                        propInfo.GetType().ToString(),
                        propInfo.Name,
                        propInfo.PropertyType.Namespace
                        )
                    );
            }
        }
    }
    finally
    {
        System.Diagnostics.Debug.Unindent();
    }
}

Answer 1

It's bad idea to dump indexer properties. It's similar to "dump method". It's just imposible.

Also consider using PropertyInfo.CanRead before trying to get value.

Answer 2

You are essentially trying to access SomeProp[foo, bar...]... so; what are sensible index values? For integers, maybe 0,0,0... is safe - maybe not. It depends on the context. Personally, I'm not sure that this is the best way to go; I might look at IList on the main object, but other than that - just look at regular properties...