访问NavigationProperty的关联详细信息

Question

我正在创建一个C＃T4模板来基于.edmx文件来构建一些类，到目前为止一直很好。我现在需要的是一种通过NavigationProperty访问它在数据库中连接的列名称的方法。

不久前，我意识到您可以在.edmx可视化设计器中，在特定NavigationProperty的映射详细信息下访问此信息：

所以基本上，如果在T4模板中;我已经有了一个我想要的NavigationProperty实例......我怎样才能获得它所连接的字段的名称？ （在这种情况下为WeatherOnMondays）

Answer 1

答案来自：EF4: Get the linked column names from NavigationProperty of an EDMX

实现这一目标的两种方法：

// Obtain a reference to the navigation property you are interested in
var navProp = GetNavigationProperty();
// Load the metadata workspace
MetadataWorkspace metadataWorkspace = null;
bool allMetadataLoaded =loader.TryLoadAllMetadata(inputFile, out metadataWorkspace);

// Get the association type from the storage model
var association = metadataWorkspace
    .GetItems<AssociationType>(DataSpace.SSpace)
    .Single(a => a.Name == navProp.RelationshipType.Name)

// Then look at the referential constraints
var toColumns = String.Join(",", 
    association.ReferentialConstraints.SelectMany(rc => rc.ToProperties));
var fromColumns = String.Join(",", 
    association.ReferentialConstraints.SelectMany(rc => rc.FromProperties));

第二种方法：

NavigationProperty[] foreignKeys = entity.NavigationProperties
  .Where(np => np.DeclaringType == entity &&
          ((AssociationType)np.RelationshipType).IsForeignKey).ToArray();

foreach (NavigationProperty foreignKey in foreignKeys)
{
   foreach(var rc in GetSourceSchemaTypes<AssociationType>()
       .Single(x => x.Name == foreignKey.RelationshipType.Name)
       .ReferentialConstraints)
   {
       foreach(var tp in rc.ToProperties)
           WriteLine(tp.Name);
       foreach(var fp in rc.FromProperties)
           WriteLine(fp.Name);
   }
}

Answer 2

如果您有NavigationProperty，则其所连接的字段由属性ToEndMember和FromEndMember

表示

Answer 3

此代码更简单。它在我的Visual Studio 2012上运行正常。可以在以下位置找到AssociationType类详细信息 http://msdn.microsoft.com/en-us/library/system.data.metadata.edm.associationtype.aspx和http://msdn.microsoft.com/en-us/library/system.data.metadata.edm.referentialconstraint.aspx。

<#@ template language="C#" debug="true" hostspecific="true"#>
<#@ include file="EF.Utility.CS.ttinclude"#>
<#
string inputFile = @"DomainModel.edmx";

MetadataLoader loader = new MetadataLoader(this);

EdmItemCollection ItemCollection = loader.CreateEdmItemCollection(inputFile);

foreach (EntityType entity in ItemCollection.GetItems<EntityType>().OrderBy(e => e.Name))
{
    foreach (NavigationProperty navProperty in entity.NavigationProperties)
    {
        AssociationType association = ItemCollection.GetItems<AssociationType>().Single(a => a.Name == navProperty.RelationshipType.Name);
        string fromEntity = association.ReferentialConstraints[0].FromRole.Name;
        string fromEntityField = association.ReferentialConstraints[0].FromProperties[0].Name;
        string toEntity = association.ReferentialConstraints[0].ToRole.Name;
        string toEntityField = association.ReferentialConstraints[0].ToProperties[0].Name;
    }
}

#>

Answer 4

请参阅http://brewdawg.github.io/Tiraggo.Edmx/，您可以从NuGet安装它。它提供edmx文件中的所有元数据，包括所有映射，每列的低级SQL数据类型，所有类型的东西，查看页面上的示例，您将看到它是多么容易。