你可以从这样的事情开始......看看这是否能把你带到任何地方。
using(ObjectContext context = new ObjectContext())
{
var queryResult = from meta in context.MetadataWorkspace.GetItems(DataSpace.CSpace)
.Where(m => m.BuiltInTypeKind == BuiltInTypeKind.EntityType)
from p in (meta as EntityType).Properties
.Where(p => p.DeclaringType.Name == context.GetType().Name
&& p.Name == PropertyName
Select new {Length = p.TypeUsage.Facets["MaxLength"].Value, Name=p.TypeUsage.Facets["Name"].Value, p.TypeUsage.Facets["FacetType"].Value
}
(@steve-cooper) 一个非常有帮助的开始!谢谢。我根据你的建议提出了一个工人阶级——我把它贴在这里,这样我就可以给你接受的答案,这样其他人就可以看到经过处理的代码。
public class ModelSummary
{
public Dictionary<string, System.Data.Metadata.Edm.EntityType> Entities { get; private set; }
public static ModelSummary Load(DbContext context)
{
var adapter = (IObjectContextAdapter)context;
var objectContext = adapter.ObjectContext;
var summary = new ModelSummary();
var items = objectContext.MetadataWorkspace.GetItems(DataSpace.SSpace);
summary.Entities =
objectContext.MetadataWorkspace.GetItems(DataSpace.SSpace)
.OfType<EntityType>()
.ToDictionary(et => et.Name);
return summary;
}
public bool EntityExists(string entityName)
{
return this.Entities.ContainsKey(entityName);
}
public bool EntityHasProperty(string entityName, string propertyName)
{
if (!EntityExists(entityName))
{
return false;
}
var entity = this.Entities[entityName];
return entity.Properties.Contains(propertyName);
}
}
测试看起来像这样;
[Test]
public void Context_SchemaIsExpected()
{
var summary = ModelSummary.Load(new MyContext());
Assert.IsTrue(summary.EntityExists("Item"));
Assert.IsTrue(summary.EntityHasProperty("Item", "Id"));
}