How Can I Dynamically Retrieve Class Attributes in C#?

Dynamicly obtain class attributes

In object-oriented programming, attributes are metadata attached to a class, providing additional information beyond the code itself. If you need to dynamically read properties at runtime, here's how to do it.

Example of domain attributes

Consider the following code snippet containing the DomainName attribute:

<code class="language-csharp">[DomainName("MyTable")]
public class MyClass : DomainBase
{ }</code>

Generic methods for attribute reading

Our goal is to create a generic method that reads the DomainName property on a given class and returns its value:

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

    if (dnAttribute != null)
    {
        return dnAttribute.Name;
    }
    return null;
}</code>

This method can be used like this:

<code class="language-csharp">string domainNameValue = GetDomainName<MyClass>(); // 返回 "MyTable"</code>

Common attribute reading

Using the AttributeExtensions class, property reading functionality can be generalized to work with any property type:

<code class="language-csharp">public static class AttributeExtensions
{
    public static TValue GetAttributeValue<TAttribute, TValue>(
        this Type type, 
        Func<TAttribute, TValue> valueSelector) 
        where TAttribute : Attribute
    {
        var att = type.GetCustomAttributes(
            typeof(TAttribute), true
        ).FirstOrDefault() as TAttribute;

        if (att != null)
        {
            return valueSelector(att);
        }
        return default(TValue);
    }
}</code>

How to use:

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

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