EF 4代码首先：由于EdmMetadata类型未包含在模型中，不能检查模型兼容性 [英] EF 4 Code First: Model compatibility cannot be checked because the EdmMetadata type was not included in the model

问题描述

我试图使用EF 4 Code First模式。我的初始化代码如下：

创建模型构建器：

  private static DbModelBuilder CreateModelBuild（）
 {
 var builder = new DbModelBuilder（）; 
 
 //添加实体类约12个
 
 builder.Conventions.Remove& IncludeMetadataConvention>（）; 
 return builder; 
} 
  

创建会话：

  private bool BuildSqlServerSession（DbModelBuilder builder）
 {
 var model = 
 builder.Build（new SqlConnection（@connection string））; 
 var cm = model.Compile（）; 
 var context = new LittlePOSContext（cm）; 
 var dbExists = context.Database.Exists（）; 
 _session = new EFSession（context）; 
 return dbExists; 
} 
  

当我第一次运行代码时，这可以工作。但是当第二次运行并尝试使用 context.Add（myEntity）添加一个对象时，我得到以下异常：

 模型兼容性无法检查，因为模型中包含EdmMetadata类型不是
。确保将IncludeMetadataConvention添加到
到DbModelBuilder约定。 
  

我尝试删除以下行：

  builder.Conventions.Remove< IncludeMetadataConvention>（）; 
  

但我仍然收到错误。

解决方案

感觉有点傻，但真正的罪魁祸首是：

 数据库。 SetInitializer（新的DropCreateDatabaseIfModelChanges< MyContext>（））; 
  

似乎 DropCreateDatabaseIfModelChanges 与 Code First 方法或者是其他一些我不明白的林业（还）。

I am trying to use EF 4 Code First pattern. My initialization code is as follows:

Create Model Builder:

private static DbModelBuilder CreateModelBuild()
{
    var builder = new DbModelBuilder();

    //add entity classes about 12 of them

    builder.Conventions.Remove<IncludeMetadataConvention>();
    return builder;
}

Create session:

private bool BuildSqlServerSession(DbModelBuilder builder)
{
    var model =
    builder.Build(new SqlConnection(@"connection string"));
    var cm = model.Compile();
    var context = new LittlePOSContext(cm);
    var dbExists = context.Database.Exists();
    _session = new EFSession(context);
    return dbExists;
}

This works when I run the code for first time. But when running on second time and trying to add an object using context.Add(myEntity) I get following exception:

Model compatibility cannot be checked because the EdmMetadata type was not 
included in the model. Ensure that IncludeMetadataConvention has been added 
to the DbModelBuilder conventions.

I have tried removing following line:

builder.Conventions.Remove<IncludeMetadataConvention>();

but I still get the error.

解决方案

Well it feels somewhat silly but the real culprit was following statement:

Database.SetInitializer(new DropCreateDatabaseIfModelChanges<MyContext>());

It seems that DropCreateDatabaseIfModelChanges is not compatible with Code First approach or it is some other mystry that I don't understand (yet).

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