Entity Framework 4: How to find the primary key?

Question

I am trying to create a generic method using EF4 to find the primary key of an object.

example

public string GetPrimaryKey()
{
    ...
}
         


        

Answer 1

I assume many people stop by this post just by looking "Entity framework how to find the primary key?" regardless EF version (like me). So I wanted to mentioned that with EF 6.1, you can also create an extension methods to get the primary key. Following is the example and works perfectly fine.

PS: I am not 100% sure, if that would work with composite and compound keys tho.

using System;
using System.Data.Entity;
using System.Data.Entity.Core.Metadata.Edm;
using System.Data.Entity.Infrastructure;
using System.Linq;

namespace System.Data.Entity
{
    public static class DbContextExtensions
    {
        public static string[] GetKeyNames(this DbContext context)
            where TEntity : class
        {
            return context.GetKeyNames(typeof(TEntity));
        }

        public static string[] GetKeyNames(this DbContext context, Type entityType)
        {
            var metadata = ((IObjectContextAdapter)context).ObjectContext.MetadataWorkspace;

            // Get the mapping between CLR types and metadata OSpace
            var objectItemCollection = ((ObjectItemCollection)metadata.GetItemCollection(DataSpace.OSpace));

            // Get metadata for given CLR type
            var entityMetadata = metadata
                    .GetItems(DataSpace.OSpace)
                    .Single(e => objectItemCollection.GetClrType(e) == entityType);

            return entityMetadata.KeyProperties.Select(p => p.Name).ToArray();
        }
    }
}

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