无法参数化Entity Framework连接字符串的问题求助

问题本质 #

你用EDMX生成的DbContext属于Database First/Model First模式，这种模式要求传入的是Entity Framework专用连接字符串（包含模型元数据信息），而你用SqlConnectionStringBuilder生成的是普通SQL Server连接字符串，EF识别不到元数据，就会默认切换到Code First模式，和你现有的EDMX模型冲突，从而抛出UnintentionalCodeFirstException。

解决方法 #

方法一：构建完整的Entity Framework连接字符串

通过EntityConnectionStringBuilder把SQL连接字符串和EDMX的元数据路径结合起来，生成符合要求的连接字符串：

private string GetEntityConnectionString()
{
    // 构建SQL Server基础连接信息
    var sqlBuilder = new SqlConnectionStringBuilder
    {
        DataSource = "localhost",
        UserID = "sa",
        Password = "1234",
        InitialCatalog = "dbtest"
    };

    // 构建EF专用连接字符串，替换Metadata里的模型名称为你的EDMX对应名称
    var entityBuilder = new EntityConnectionStringBuilder
    {
        Provider = "System.Data.SqlClient",
        ProviderConnectionString = sqlBuilder.ConnectionString,
        // 元数据路径可直接复制app.config中原有EF连接字符串的Metadata部分
        Metadata = "res://*/tallerdemecanicaModel.csdl|res://*/tallerdemecanicaModel.ssdl|res://*/tallerdemecanicaModel.msl"
    };

    return entityBuilder.ConnectionString;
}

修改测试代码调用该方法：

private void button1_Click(object sender, EventArgs e)
{
    using (tallerdemecanicaEntities db = new tallerdemecanicaEntities(GetEntityConnectionString()))
    {
        var list = db.vta_factura.ToList();
        dataGridView1.DataSource = list;
    }
}

方法二：直接传入EntityConnection对象

创建EntityConnection实例并传给DbContext（需确保DbContext有接收DbConnection的构造函数）：

private EntityConnection GetEntityConnection()
{
    var sqlBuilder = new SqlConnectionStringBuilder
    {
        DataSource = "localhost",
        UserID = "sa",
        Password = "1234",
        InitialCatalog = "dbtest"
    };

    var entityBuilder = new EntityConnectionStringBuilder
    {
        Provider = "System.Data.SqlClient",
        ProviderConnectionString = sqlBuilder.ConnectionString,
        Metadata = "res://*/tallerdemecanicaModel.csdl|res://*/tallerdemecanicaModel.ssdl|res://*/tallerdemecanicaModel.msl"
    };

    return new EntityConnection(entityBuilder.ConnectionString);
}

测试代码调用：

private void button1_Click(object sender, EventArgs e)
{
    using (var connection = GetEntityConnection())
    // 第二个参数false表示不接管连接生命周期，由using块负责释放
    using (tallerdemecanicaEntities db = new tallerdemecanicaEntities(connection, false))
    {
        var list = db.vta_factura.ToList();
        dataGridView1.DataSource = list;
    }
}

注意事项 #

• 元数据路径中的模型名称要和你的EDMX文件名一致，不确定的话可以打开app.config，复制原有EF连接字符串里的Metadata部分直接使用。
• 如果你的DbContext没有接收DbConnection的构造函数，需要手动添加：

  public tallerdemecanicaEntities(DbConnection connection, bool contextOwnsConnection) 
      : base(connection, contextOwnsConnection)
  {
  }
  

内容的提问来源于stack exchange，提问作者jebus