Reflection

Microsoft .NET Framework, ASP.NET, Visual C# (CSharp, C Sharp, C-Sharp) Developer Training, Visual Studio

Reflection—in object-oriented language—allows programmatic inspection of a class to find out all the information about it. In C#, reflection allows you to look inside an assembly, including all the object types contained within it. The reflection objects can be found in System.Reflection namespace.

Contents 1 Example 1.1 Base Code 1.2 Hardcoded 1.3 Dynamic 1.4 Output 2 See also

Example

Reflection is a very powerful tool, take for example the following scenario:

You want to print to a textbox some information about a person, but the type of information stored is expected to change very soon...

This type of situation is extremely common for a programmer working in a real-life situation where the application is developing as it travels round the development cycle. The information we know we want to store is:

• Name
• Age
• Sex
• SpecialInfomation

Base Code

using System.Reflection;
 
Person m_PersonA = new Person();
 
public struct Person
{
   public String Name;
   public Byte Age;
   public String Sex;
   public String SpecialInfomation;
}
 
private void Form1_Load(object sender, EventArgs e)
{
   m_PersonA.Name = "Bill";
   m_PersonA.Age = 24;
   m_PersonA.Sex = "Male";
   m_PersonA.SpecialInfomation = "Not much really";
}

Hardcoded

You may be tempted to hard code the information which is stored knowing full well that you will later have to change it.

private void button1_Click(object sender, EventArgs e)
{
   StringBuilder non_reflectedText = new StringBuilder();
 
   non_reflectedText.Append(String.Format("Name: {0}\r\n",m_PersonA.Name));
   non_reflectedText.Append(String.Format("Age: {0}\r\n", m_PersonA.Age));
   non_reflectedText.Append(String.Format("Sex: {0}\r\n", m_PersonA.Sex));
   non_reflectedText.Append(String.Format("SpecialInfomation: {0}\r\n",
      m_PersonA.SpecialInfomation));
 
   textBox1.AppendText(non_reflectedText.ToString());
 }

Dynamic

But let’s not make work for ourselves, instead let’s get the VES (Virtual Execution System) when running the code, find out what information is stored.

private void button1_Click(object sender, EventArgs e)
{
   StringBuilder reflectedText = new StringBuilder();
   Type programDataType = m_PersonA.GetType();
 
   foreach (FieldInfo member in programDataType.GetFields())
   {
      reflectedText.Append(String.Format("{0}: {1}\r\n",
         member.Name,member.GetValue(m_PersonA)));
   }
 
   textBox1.AppendText(reflectedText.ToString());
}

Output

Now when the struct is updated to hold new or different information the dynamic code will automatically show the new members of the struct along with the data.

See also

• .NET Metadata