Question

I’m writing some code for a class constructor which loops through all the properties of the class and calls a generic static method which populates my class with data from an external API. So I’ve got this as an example class:

public class MyClass{   public string Property1 { get; set; }   public int Property2 { get; set; }   public bool Property3 { get; set; }    public static T DoStuff<T>(string name){     // get the data for the property from the external API     // or if there's a problem return 'default(T)'   } } 

Now in my constructor I want something like this:

public MyClass(){   var properties = this.GetType().GetProperties();   foreach(PropertyInfo p in properties){     p.SetValue(this, DoStuff(p.Name), new object[0]);   } } 

So the above constructor will thrown an error because I’m not supplying the generic type.

So how do I pass in the type of the property in?

Answer 1

Do you want to call DoStuff<T> with T = the type of each property? In which case, ‘as is’ you would need to use reflection and MakeGenericMethod – i.e.

var properties = this.GetType().GetProperties(); foreach (PropertyInfo p in properties) {     object value = typeof(MyClass)     .GetMethod('DoStuff')     .MakeGenericMethod(p.PropertyType)     .Invoke(null, new object[] { p.Name });     p.SetValue(this, value, null); } 

However, this isn’t very pretty. In reality I wonder if it wouldn’t be better just to have:

static object DoStuff(string name, Type propertyType); ... and then object value = DoStuff(p.Name, p.PropertyType); 

What does the generics give you in this example? Note that value-types will still get boxed etc during the reflection call – and even then boxing isn’t as bad as you might think.

Finally, in many scenarios, TypeDescriptor.GetProperties() is more appropriate than Type.GetProperties() – allows for flexible object models etc.