Setting a property by reflection with a string value

user_62151 0
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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?

setvalue propertyinfo type-conversion reflection c#
12 Answers

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);
user_916710

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!

John_Saunders_763370

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);
John_Calsbeek_56960

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

propertyInfo.SetValue( ship,
                       Convert.ChangeType( value, propertyInfo.PropertyType ),
                       null );
user_129500

I will answer this with a general answer. Usually these answers not working with guids. Here is a working version with guids too.

var stringVal="6e3ba183-89d9-e611-80c2-00155dcfb231"; // guid value as string to set
var prop = obj.GetType().GetProperty("FooGuidProperty"); // property to be setted
var propType = prop.PropertyType;

// var will be type of guid here
var valWithRealType = TypeDescriptor.GetConverter(propType).ConvertFrom(stringVal);
user_14172140

Or you could try:

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

//But this will cause problems if your string value IsNullOrEmplty...
user_864520

Using the following code should solve your issue:

item.SetProperty(prop.Name, Convert.ChangeType(item.GetProperty(prop.Name).ToString().Trim(), prop.PropertyType));
user_115931520

Are you looking to play around with Reflection or are you looking to build a production piece of software? I would question why you're using reflection to set a property.

Double new_latitude;

Double.TryParse (value, out new_latitude);
ship.Latitude = new_latitude;
user_459380
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