Cast object to T

Question

I\'m parsing an XML file with the XmlReader class in .NET and I thought it would be smart to write a generic parse function to read different attributes generic

Answer 1

You can presumably pass-in, as a parameter, a delegate which will convert from string to T.

Answer 2

Have you tried Convert.ChangeType?

If the method always returns a string, which I find odd, but that's besides the point, then perhaps this changed code would do what you want:

private static T ReadData<T>(XmlReader reader, string value)
{
    reader.MoveToAttribute(value);
    object readData = reader.ReadContentAsObject();
    return (T)Convert.ChangeType(readData, typeof(T));
}

Answer 3

Add a 'class' constraint (or more detailed, like a base class or interface of your exepected T objects):

private static T ReadData<T>(XmlReader reader, string value) where T : class
{
    reader.MoveToAttribute(value);
    object readData = reader.ReadContentAsObject();
    return (T)readData;
}

or where T : IMyInterface or where T : new(), etc

Answer 4

try

if (readData is T)
    return (T)(object)readData;

Answer 5

First check to see if it can be cast.

if (readData is T) {
    return (T)readData;
} 
try {
   return (T)Convert.ChangeType(readData, typeof(T));
} 
catch (InvalidCastException) {
   return default(T);
}

Answer 6

Actually, the problem here is the use of ReadContentAsObject. Unfortunately, this method does not live up to its expectations; while it should detect the most appropirate type for the value, it actually returns a string, no matter what(this can be verified using Reflector).

However, in your specific case, you already know the type you want to cast to, therefore i would say you are using the wrong method.

Try using ReadContentAs instead, it's exactly what you need.

private static T ReadData<T>(XmlReader reader, string value)
{
    reader.MoveToAttribute(value);
    object readData = reader.ReadContentAs(typeof(T), null);
    return (T)readData;
}