实体框架4:通用存储库:如何确定EntitySetName？

Question

如果您为Entity Framework 4中的实体执行通用存储库,则首先要查询实体:

public IEnumerable<E> GetEntity()
{
    return _container.CreateQuery<E>( ... );
}

在...上面我们需要EntitySetName,它通常是复数形式E的名称.然而,它并不总是像添加's'一样容易.例如,如果我们只添加一个's',这将有效.

    return _container.CreateQuery<E>( "[" + typeof(E).Name + "s]");

如果我们有一个真实的实体,这将包含我们的EntitySetName:

E.EntityKey.EntitySetName

当只提供E类型时,如何获取EntitySetName？

Answer 1

这很棘手,特别是涉及代理时,但可能.以下是我在Halfpipe中的表现:

    /// <summary>
    /// Returns entity set name for a given entity type
    /// </summary>
    /// <param name="context">An ObjectContext which defines the entity set for entityType. Must be non-null.</param>
    /// <param name="entityType">An entity type. Must be non-null and have an entity set defined in the context argument.</param>
    /// <exception cref="ArgumentException">If entityType is not an entity or has no entity set defined in context.</exception>
    /// <returns>String name of the entity set.</returns>
    internal static string GetEntitySetName(this ObjectContext context, Type entityType)
    {
        if (context == null)
        {
            throw new ArgumentNullException("context");
        }
        if (entityType == null)
        {
            throw new ArgumentNullException("entityType");
        }
        // when POCO proxies are enabled, "entityType" may be a subtype of the mapped type.
        Type nonProxyEntityType = ObjectContext.GetObjectType(entityType);
        if (entityType == null)
        {
            throw new ArgumentException(
                string.Format(System.Globalization.CultureInfo.CurrentUICulture,
                Halfpipe.Resource.TypeIsNotAnEntity,
                entityType.Name));
        }

        var container = context.MetadataWorkspace.GetEntityContainer(context.DefaultContainerName, System.Data.Metadata.Edm.DataSpace.CSpace);
        var result = (from entitySet in container.BaseEntitySets
                      where entitySet.ElementType.Name.Equals(nonProxyEntityType.Name)
                      select entitySet.Name).SingleOrDefault();
        if (string.IsNullOrEmpty(result))
        {
            throw new ArgumentException(
                string.Format(System.Globalization.CultureInfo.CurrentUICulture,
                Halfpipe.Resource.TypeIsNotAnEntity,
                entityType.Name));
        }
        return result;
    }