CODEWITHSUNDEEP
c#reflection
johnc
johnc

Reputation: 40223

C# setting property values through reflection with attributes

I am trying to build an object through an attribute on a classes property that specifies a column in a supplied data row that is the value of the property, as below:

    [StoredDataValue("guid")]
    public string Guid { get; protected set; }

    [StoredDataValue("PrograGuid")]
    public string ProgramGuid { get; protected set; }

In a Build() method on a base object, I am getting the attribute values set on these properties as

        MemberInfo info = GetType();
        object[] properties = info.GetCustomAttributes(true);

However, at this point I am realising the limitation in my knowledge.

For a start, I don't appear to be getting back the correct attributes.

And how do I set these properties through reflection, now that I have the attributes? Am I doing / thinking something fundamentally incorrect?

Upvotes: 22

Views: 45525

Answers (1)

Tamas Czinege
Tamas Czinege

Reputation: 121314

There are a couple of separate issues here

  • typeof(MyClass).GetCustomAttributes(bool) (or GetType().GetCustomAttributes(bool)) returns the attributes on the class itself, not the attributes on members. You will have to invoke typeof(MyClass).GetProperties() to get a list of properties in the class, and then check each of them.

  • Once you got the property, I think you should use Attribute.GetCustomAttribute() instead of MemberInfo.GetGustomAttributes() since you exactly know what attribute you are looking for.

Here's a little code snippet to help you start:

PropertyInfo[] properties = typeof(MyClass).GetProperties();
foreach(PropertyInfo property in properties)
{
    StoredDataValueAttribute attribute =
        Attribute.GetCustomAttribute(property, typeof(StoredDataValueAttribute)) as StoredDataValueAttribute;

    if (attribute != null) // This property has a StoredDataValueAttribute
    {
         property.SetValue(instanceOfMyClass, attribute.DataValue, null); // null means no indexes
    }
}

EDIT: Don't forget that Type.GetProperties() only returns public properties by default. You will have to use Type.GetProperties(BindingFlags) to get other sorts of properties as well.

Upvotes: 44

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