Add custom attribute to a class generated by Entity Framework

Question

I am trying to use a custom attribute on a Entity class generated automatically by the Entity Framework.

The problem is how to add an property attribute on an existing field?

Here the point where I am right now:

// the custom attribute class
public class MyCustomAttribute : Attribute
{
    public String Key { get; set; }
}

// Entity Framework class generated automatically
public partial class EntityClass
{  
    public String Existent { get; set; }
    //...
}

// set a metadata class for my entity
[MetadataType(typeof(EntityClassMetaData))]
public partial class EntityClass
{
    // if I add a new property to the entity, it works. This attribute will be read
    [MyCustomAttribute(Key = "KeyOne" )]
    public int newProp { get; set; }
}

public class EntityClassMetaData
{
    // adding the custom attribute to the existing property
    [MyCustomAttribute(Key = "keyMeta") ]
    public String Existent { get; set; }    
}

Running this test:

[TestMethod]
public void test1()
{
        foreach (var prop in typeof(EntityClass).GetProperties())
        {
            var att = prop.GetCustomAttribute<MyCustomAttribute>();

            if (att != null)
            {
                Console.WriteLine($"Found {att.Key}");
            }
        }                    
}

will produce:

Found KeyOne

Or the Metadata class store the attribute in a different way or only works for data annotations.

I am stuck here, how can I set and read custom attributes of the generated class without having to edit the generated file?

mj2711 · Accepted Answer · 2018-07-17 14:18:37Z

I came across this same problem today. I figured EF magic would do the trick and map the attribute across to each model property. Turns out it does, but only for EF data annotations and I couldn't find an answered solution to pull out custom attributes so made this function. Hope it helps dude.

private object[] GetMetadataCustomAttributes(Type T, string propName)
    {
        if (Attribute.IsDefined(T, typeof(MetadataTypeAttribute)))
        {
            var metadataClassType = 
            (T.GetCustomAttributes(typeof(MetadataTypeAttribute), true).FirstOrDefault() as 
            MetadataTypeAttribute).MetadataClassType;
            var metaDataClassProperty = metadataClassType.GetProperty(propName);
            if (metaDataClassProperty != null)
            {
                return metaDataClassProperty.GetCustomAttributes(true);
            }
        }
        return null;
    }

marc_s · Accepted Answer · 2018-03-09 19:07:36Z

0

I believe if you want to set an attribute in the metadata class, you have to use this syntax:

public class EntityClassMetaData
{
    // adding the custom attribute to the existing property
    [MyCustomAttribute(Key = "keyMeta") ]
    public String Existent;  
}

You must not have { get; set; } on your pre-existing property - just the property with the correct name and datatype.

answered Mar 9, 2018 at 19:07

marc_s

760k186 gold badges1.4k silver badges1.5k bronze badges

1 Comment

MiguelSlv Over a year ago

Nope. Tested with that change but got the same result

Collectives™ on Stack Overflow

Add custom attribute to a class generated by Entity Framework

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related