ASP.Net Linq to Entities：无法加载指定的元数据资源。- EntityConnectionStringBuilder

Question

我已经阅读了很多帖子，但这似乎非常有用，但我不确定我是否理解如何实现这个解决方案。我是否应该将此代码放入使用实体模型的每个类中？我已经阅读了 Microsoft 文档，我想我对此还太陌生。

我的实体模型位于我的 DATALAYER 中，这是一个单独的项目。我还有业务逻辑层和用户界面层。从我收集到的信息来看，问题似乎与我的实体模型位于不同的项目中这一事实有关。是这样吗？提前致谢！

来自另一篇文章构造连接字符串的更好方法是使用EntityConnectionStringBuilder：

public static string GetSqlCeConnectionString(string fileName) 
{ 
    var csBuilder = new EntityConnectionStringBuilder(); 

    csBuilder.Provider = "System.Data.SqlServerCe.3.5"; 
    csBuilder.ProviderConnectionString = string.Format("Data Source={0};", fileName); 

    csBuilder.Metadata = string.Format("res://{0}/YourEdmxFileName.csdl|res://{0}/YourEdmxFileName.ssdl|res://{0}/YourEdmxFileName.msl",  
        typeof(YourObjectContextType).Assembly.FullName); 

    return csBuilder.ToString(); 
} 

public static string GetSqlConnectionString(string serverName, string databaseName) 
{ 
    SqlConnectionStringBuilder providerCs = new SqlConnectionStringBuilder(); 

    providerCs.DataSource = serverName; 
    providerCs.InitialCatalog = databaseName; 
    providerCs.IntegratedSecurity = true; 

    var csBuilder = new EntityConnectionStringBuilder(); 

    csBuilder.Provider = "System.Data.SqlClient"; 
    csBuilder.ProviderConnectionString = providerCs.ToString(); 

    csBuilder.Metadata = string.Format("res://{0}/YourEdmxFileName.csdl|res://{0}/YourEdmxFileName.ssdl|res://{0}/YourEdmxFileName.msl", 
        typeof(YourObjectContextType).Assembly.FullName); 

    return csBuilder.ToString(); 
} 

Answer 1

您可以将连接详细信息移至配置文件吗？这是一篇关于连接字符串的文章。并遵循与本文中相同的示例，这里是上下文的初始化和使用：

using (EntityConnection connection =  EntityConnection("name=AdventureWorksEntities"))
{
    AdventureWorksEntities context = new AdventureWorksEntities(connection);
    context.AddObject("Customer", customer);
    context.SaveChanges();
}

编辑：无需在调用客户端中重复连接构建代码。您应该向呼叫者隐藏这些详细信息。以下是返回新对象上下文的工厂示例：

//app.config
<connectionStrings>
    <add name="TestEntities" connectionString="...." />
</connectionStrings>

//data entities
public partial class TestEntities : ObjectContext
{
    public TestEntities() : base("name=TestEntities", "TestEntities")
    {
        ...
    }
    ....
}

//factory in Data Access layer
public sealed class TestEntitiesFactory
{
    public static Func<TestEntities> GetNewTestEntitiesInstance { get; set; }

    static TestEntitiesFactory()
    {
        GetNewTestEntitiesInstance = TestEntitiesCreator.CreateTestEntities;
    }
}

public sealed class TestEntitiesDefaultCreator
{
    public static TestEntities CreateTestEntities()
    {
        TestEntities test = new TestEntities();

        //whatever initializations you need

        return test;
    }
}

//business layer
using (TestEntities ctx = TestEntitiesFactory.GetNewTestEntitiesInstance())
{

}