使用自定义的ConnectionString和DbProviderInfo创建DbContext

问题描述

我们有大量数据库共享相同的模式。它们分布在许多SQL Server上，一些是2005年，一些是2008年。当连接到2005服务器之后连接到一个2005服务器时，我们遇到了一个例外，首先说明如下：

所以据了解，是根据2008年SQL服务器提供商信息创建的模型，因此当连接到2005服务器时，它不能使用DateTime2数据类型，因为它不支持。

我们希望针对2005服务器构建模型，但我不确定如何指定连接字符串和DbCompiledModel。以前我有几个构造函数使用连接字符串（包括其他参数）...

  public ProjectContext（string ConnectionString ）：base（ConnectionString）
 {
 
 //获取与此DbContext相关的ObjectContext 
 var objectContext =（这作为IObjectContextAdapter）.ObjectContext; 
 
 // ...使用ObjectContext 
 
  

如何为所有上下文（最低公分母）指定针对2005服务器构建的编译模型，并指定连接字符串？我只是没有看到这样做的方式。

任何帮助将不胜感激。

编辑：
我们正在使用实体框架4.3代码，因此，没有一个设计时间的EDMX文件进行编辑。

解决方案

基类构造函数有一个重载！

我将OnModelCreating配置文件复制到一个返回名为BuildModel的DbCompiledModel的新方法中。当调用了具有ConnectionString构造函数的构造函数时，我获取了dbModel的值，这是一个私有readonly属性，如果为null，则将其设置为从BuildModel返回的值。属性值与连接字符串一起提供给基类​​构造函数。

我可以访问我要连接的SQL Server版本。最终我会把它引入并创建一个模型为2005年，一个在2008年。

我将离开这个开放一段时间，以防万一有更好的方法这个。

  public DbContext ProjectContext（string ConnectionString）
：base（ConnectionString，dbModel）
 {
 
} 
 
 private DbCompiledModel _dbModel; 
 private DbCompiledModel dbModel; 
 {
 get 
 {
 if（_dbModel == null）
 {
 _dbModel = BuildModel（new DbModelBuilder（））; 
} 
 return _dbModel; 
} 
 
 
 private DbCompiledModel BuildModel（DbModelBuilder builder）
 {
 //一些配置东西
 return builder.Build（new DbProviderInfo （System.Data.SqlClient，2005））
 .Compile（）; 
} 
  

We have a plethora of databases all sharing the same schema. They are spread about on a number of SQL Servers, some 2005, some 2008. We are getting an exception when connecting to a 2005 server AFTER having connected to a 2008 server first stating the following:

So as I understand it what is happening is the Model is being created according to a 2008 SQL servers provider info, and thus when connected to a 2005 server, it can't use the DateTime2 data type because that is not supported there.

We would like to build the model against a 2005 server, but I am unsure of how to specify both the connection string AND the DbCompiledModel. Previously I have had a couple of constructors that take the connection string (among other parameters)...

    public ProjectContext(string ConnectionString) : base(ConnectionString)
    {

        // Get the ObjectContext related to this DbContext
        var objectContext = (this as IObjectContextAdapter).ObjectContext;

        // ... does some stuff with the ObjectContext
    }

How can I specify the compiled model built against a 2005 server for ALL contexts (lowest common denominator) and also specify the connection string? I just don't see a way to do it at the moment.

Any help would be appreciated.

Edit:We are using Entity Framework 4.3 Code First, thus, there is not a design time EDMX file to edit.

解决方案

There is an overload for the base class constructor!

I copied my OnModelCreating configuration stuff into a new method that returns DbCompiledModel named BuildModel. When my constructor that has ConnectionString constructor is called, I get the value of dbModel, a private readonly property which if null, gets set to the value returned from BuildModel. The property value gets fed to the base class constructor along with the connection string.

I have access to the SQL server versions that I am connecting to. Eventually I will bring that in and create one model for 2005 and one for 2008.

I will leave this open for a while just in case there is a better way to do this.

public DbContext ProjectContext (string ConnectionString) 
    : base(ConnectionString, dbModel)
{

}

private DbCompiledModel _dbModel;
private DbCompiledModel dbModel;
{
    get
    {
        if (_dbModel == null)
        {
            _dbModel = BuildModel(new DbModelBuilder());
        }
        return _dbModel;
    }
}

    private DbCompiledModel BuildModel(DbModelBuilder builder)
    {
        //Some configuration stuff
        return builder.Build(new DbProviderInfo("System.Data.SqlClient", "2005"))
                      .Compile();
    }

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