Question

我按照这个例子Changing schema name on runtime - Entity Framework在那里我可以从MetaDataWorkspace创建一个新的EntityConnection，然后我用它来构建一个具有不同模式的DbContext，但是我收到编译器警告说RegisterItemCollection方法已经过时并且“构造” MetadataWorkspace使用接受元数据加载委托的构造函数。“

我该怎么做？这是正在运行的代码，但为RegsiterItemCollection调用提供了3个警告。我很惊讶它有效，因为警告说过时不仅仅是弃用了。

        public static EntityConnection CreateEntityConnection(string schema, string connString, string model)
    {
        XmlReader[] conceptualReader = new XmlReader[]
        {
            XmlReader.Create(
                Assembly
                    .GetExecutingAssembly()
                    .GetManifestResourceStream(model + ".csdl")
            )
        };

        XmlReader[] mappingReader = new XmlReader[]
        {
            XmlReader.Create(
                Assembly
                    .GetExecutingAssembly()
                    .GetManifestResourceStream(model + ".msl")
            )
        };

        var storageReader = XmlReader.Create(
            Assembly
                .GetExecutingAssembly()
                .GetManifestResourceStream(model + ".ssdl")
        );
        //XNamespace storageNS = "http://schemas.microsoft.com/ado/2009/02/edm/ssdl"; // this would not work!!!
        XNamespace storageNS = "http://schemas.microsoft.com/ado/2009/11/edm/ssdl";

        var storageXml = XElement.Load(storageReader);

        foreach (var entitySet in storageXml.Descendants(storageNS + "EntitySet"))
        {
            var schemaAttribute = entitySet.Attributes("Schema").FirstOrDefault();
            if (schemaAttribute != null)
            {
                schemaAttribute.SetValue(schema);
            }
        }
        storageXml.CreateReader();

        StoreItemCollection storageCollection =
            new StoreItemCollection(
                new XmlReader[] { storageXml.CreateReader() }
            );
        EdmItemCollection conceptualCollection = new EdmItemCollection(conceptualReader);
        StorageMappingItemCollection mappingCollection =
            new StorageMappingItemCollection(
                conceptualCollection, storageCollection, mappingReader
            );

        //var workspace2 = new MetadataWorkspace(conceptualCollection, storageCollection, mappingCollection);
        var workspace = new MetadataWorkspace();
        workspace.RegisterItemCollection(conceptualCollection);
        workspace.RegisterItemCollection(storageCollection);
        workspace.RegisterItemCollection(mappingCollection);

        var connectionData = new EntityConnectionStringBuilder(connString);
        var connection = DbProviderFactories
            .GetFactory(connectionData.Provider)
            .CreateConnection();
        connection.ConnectionString = connectionData.ProviderConnectionString;

        return new EntityConnection(workspace, connection);
    }

Answer 1

我能够摆脱3条警告信息。基本上，它希望您在MetadataWorkspace的构造函数中注册集合。

MetadataWorkspace有3种不同的重载，我选择使用需要为工作空间元数据提供路径（字符串数组）的重载。为此，我将读者保存到临时文件并重新加载。

这对我没有任何警告。

public static EntityConnection CreateEntityConnection(string schema, string connString, string model) {

        var conceptualReader = XmlReader.Create(Assembly.GetExecutingAssembly().GetManifestResourceStream(model + ".csdl"));
        var mappingReader = XmlReader.Create(Assembly.GetExecutingAssembly().GetManifestResourceStream(model + ".msl"));
        var storageReader = XmlReader.Create(Assembly.GetExecutingAssembly().GetManifestResourceStream(model + ".ssdl"));

        XNamespace storageNS = "http://schemas.microsoft.com/ado/2009/11/edm/ssdl";

        var storageXml = XElement.Load(storageReader);
        var conceptualXml = XElement.Load(conceptualReader);
        var mappingXml = XElement.Load(mappingReader);

        foreach (var entitySet in storageXml.Descendants(storageNS + "EntitySet")) {
            var schemaAttribute = entitySet.Attributes("Schema").FirstOrDefault();
            if (schemaAttribute != null) {
                schemaAttribute.SetValue(schema);
            }
        }

        storageXml.Save("temp.ssdl");
        conceptualXml.Save("temp.csdl");
        mappingXml.Save("temp.msl");

        MetadataWorkspace workspace = new MetadataWorkspace(new List<String>(){
                                                                @"temp.csdl",
                                                                @"temp.ssdl",
                                                                @"temp.msl"
                                                        } 
                                                       ,  new List<Assembly>());


        var connectionData = new EntityConnectionStringBuilder(connString);
        var connection = DbProviderFactories.GetFactory(connectionData.Provider).CreateConnection();
        connection.ConnectionString = connectionData.ProviderConnectionString;

        return new EntityConnection(workspace, connection);

    }

Answer 2

不想创建减慢进程的临时文件，我发现另一个答案很简单。我替换了这些代码行 -

    //var workspace2 = new MetadataWorkspace(conceptualCollection, storageCollection, mappingCollection);
    var workspace = new MetadataWorkspace();
    workspace.RegisterItemCollection(conceptualCollection);
    workspace.RegisterItemCollection(storageCollection);
    workspace.RegisterItemCollection(mappingCollection);

使用这一行代码 -

    var workspace = new MetadataWorkspace(() => conceptualCollection, () => storageCollection, () => mappingCollection);

并且工作正常。

如何使用元数据加载委托创建MetadataWorkspace？

2 个答案: