Setting a property by reflection with a string val

Question

I'd like to set a property of an object through Reflection, with a value of type string. So, for instance, suppose I have a Ship class, with a property of Latitude, which is a double.

Here's what I'd like to do:

Ship ship = new Ship();
string value = "5.5";
PropertyInfo propertyInfo = ship.GetType().GetProperty("Latitude");
propertyInfo.SetValue(ship, value, null);

As is, this throws an ArgumentException:

Object of type 'System.String' cannot be converted to type 'System.Double'.

How can I convert value to the proper type, based on propertyInfo?

Answer 1

As several others have said, you want to use Convert.ChangeType:

propertyInfo.SetValue(ship,
    Convert.ChangeType(value, propertyInfo.PropertyType),
    null);

In fact, I recommend you look at the entire Convert Class.

This class, and many other useful classes are part of the System Namespace. I find it useful to scan that namespace every year or so to see what features I've missed. Give it a try!

Answer 2

If you are writing Metro app, you should use other code:

Ship ship = new Ship();
string value = "5.5";
PropertyInfo propertyInfo = ship.GetType().GetTypeInfo().GetDeclaredProperty("Latitude");
propertyInfo.SetValue(ship, Convert.ChangeType(value, propertyInfo.PropertyType));

Note:

ship.GetType().GetTypeInfo().GetDeclaredProperty("Latitude");

instead of

ship.GetType().GetProperty("Latitude");

Answer 3

Using Convert.ChangeType and getting the type to convert from the PropertyInfo.PropertyType.

propertyInfo.SetValue( ship,
                       Convert.ChangeType( value, propertyInfo.PropertyType ),
                       null );

Answer 4

You're probably looking for the Convert.ChangeType method. For example:

Ship ship = new Ship();
string value = "5.5";
PropertyInfo propertyInfo = ship.GetType().GetProperty("Latitude");
propertyInfo.SetValue(ship, Convert.ChangeType(value, propertyInfo.PropertyType), null);

Answer 5

You can use Convert.ChangeType() - It allows you to use runtime information on any IConvertible type to change representation formats. Not all conversions are possible, though, and you may need to write special case logic if you want to support conversions from types that are not IConvertible.

The corresponding code (without exception handling or special case logic) would be:

Ship ship = new Ship();
string value = "5.5";
PropertyInfo propertyInfo = ship.GetType().GetProperty("Latitude");
propertyInfo.SetValue(ship, Convert.ChangeType(value, propertyInfo.PropertyType), null);

Answer 6

Or you could try:

propertyInfo.SetValue(ship, Convert.ChangeType(value, propertyInfo.PropertyType), null);

//But this will cause problems if your string value IsNullOrEmplty...