C# Tutorial "Introduction to Reflection API" : FieldInfo

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Introduction to Reflection API

FieldInfo

FieldInfo class discovers the attributes of a field and provides access to field metadata.

To get a list of public fields in an object, we'll use Type's GetFields method:

Type myObjectType = typeof(MyObject);

System.Reflection.FieldInfo[] fieldInfo = myObjectType.GetFields();
​x
 
Type myObjectType = typeof(MyObject);
​
System.Reflection.FieldInfo[] fieldInfo = myObjectType.GetFields();

The FieldInfo class that gets returned actually contains a lot of useful information. It also contains the ability to set that field on an instance of object- that's where the real power comes in.

Other properties and methods you can check on MSDN

Example

Set instance field values using Reflection API

 
using System;
​
class MyClass
{
    public string myString;
    
    public MyClass myInstance;
    
    public int myInt;
}
                    
public class Program
{
    public static void Main()
    {
        Type myType = typeof(MyClass);
​
        System.Reflection.FieldInfo[] fieldInfo = myType.GetFields();
        
        MyClass myClass = new MyClass();
​
        foreach (System.Reflection.FieldInfo info in fieldInfo)
        {
           switch (info.Name)
           {
              case "myString":
                 info.SetValue(myClass, "string value");
                 break;
              case "myInt":
                 info.SetValue(myClass, 42);
                 break;
              case "myInstance":
                 info.SetValue(myClass, myClass);
                 break;
           }
        }
        
        //read back the field information
        foreach (System.Reflection.FieldInfo info in fieldInfo)
        {
           Console.WriteLine(info.Name + ": " + 
              info.GetValue(myClass).ToString());
        }
    }
}