How Can I Dynamically Retrieve Attribute Values from a Class at Runtime?

Retrieve properties at runtime

This article introduces a general method for dynamically accessing and extracting attribute values ​​​​of a class.

Use dedicated methods

Define a generic method that accepts type parameters:

<code class="language-csharp">public string GetDomainName<T>()</code>

Internal method:

• Use typeof(T).GetCustomAttributes to retrieve custom properties:

  <code class="language-csharp">  var dnAttribute = typeof(T).GetCustomAttributes(
      typeof(DomainNameAttribute), true
    ).FirstOrDefault() as DomainNameAttribute;</code>

• If the attribute exists, return its value:

  <code class="language-csharp">  if (dnAttribute != null)
    {
      return dnAttribute.Name;
    }</code>

• Otherwise, return null:

  <code class="language-csharp">  return null;</code>

Utility extension methods

For wider applicability, generalize this method to handle any attribute:

<code class="language-csharp">public static class AttributeExtensions
{
    public static TValue GetAttributeValue<TAttribute, TValue>(
        this Type type, 
        Func<TAttribute, TValue> valueSelector) 
        where TAttribute : Attribute
}</code>

Internal extension method:

• Retrieve custom attributes:

  <code class="language-csharp">  var att = type.GetCustomAttributes(
      typeof(TAttribute), true
    ).FirstOrDefault() as TAttribute;</code>

• If the attribute exists, use the provided valueSelector to extract the required value:

  <code class="language-csharp">  if (att != null)
    {
      return valueSelector(att);
    }</code>

• Otherwise, return the default value of the type:

  <code class="language-csharp">  return default(TValue);</code>

Usage examples

• Retrieve the MyClass attribute of DomainName:

<code class="language-csharp">string name = typeof(MyClass).GetDomainName<MyClass>();</code>

• Retrieve any attribute value of MyClass using extension methods:

<code class="language-csharp">string name = typeof(MyClass)
    .GetAttributeValue<DomainNameAttribute, string>((DomainNameAttribute dna) => dna.Name);</code>

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