我已经看到大多数人在使用SingleOrDefault
时都会收到此错误。但是,我正在使用FirstOrDefault
。以前有人见过这种异常吗?我正在使用存储库模式以使用依赖注入。
return context.Users.FirstOrDefault(p => p.Username.ToLower() == username.ToLower());
见下文:错误来自EntityFramework的内部代码。我可以告诉你。
[InvalidOperationException: Sequence contains more than one matching element]
System.Linq.Enumerable.SingleOrDefault(IEnumerable`1 source, Func`2 predicate) +2668318
System.Data.Entity.ModelConfiguration.Conventions.IdKeyDiscoveryConventionImpl.MatchKeyProperty(EdmEntityType entityType, IEnumerable`1 primitiveProperties) +121
System.Data.Entity.ModelConfiguration.Conventions.KeyDiscoveryConvention.System.Data.Entity.ModelConfiguration.Conventions.IEdmConvention<System.Data.Edm.EdmEntityType>.Apply(EdmEntityType entityType, EdmModel model) +72
System.Data.Entity.ModelConfiguration.Conventions.IdKeyDiscoveryConvention.System.Data.Entity.ModelConfiguration.Conventions.IEdmConvention<System.Data.Edm.EdmEntityType>.Apply(EdmEntityType entityType, EdmModel model) +17
System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.Dispatch(TEdmDataModelItem item) +100
System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.VisitEdmEntityType(EdmEntityType item) +22
System.Data.Edm.Internal.DataModelItemVisitor.VisitCollection(IEnumerable`1 collection, Action`1 visitMethod) +138
System.Data.Edm.Internal.EdmModelVisitor.VisitEntityTypes(EdmNamespace edmNamespace, IEnumerable`1 entityTypes) +75
System.Data.Edm.Internal.EdmModelVisitor.VisitEdmNamespace(EdmNamespace item) +88
System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.VisitEdmNamespace(EdmNamespace item) +31
System.Data.Edm.Internal.DataModelItemVisitor.VisitCollection(IEnumerable`1 collection, Action`1 visitMethod) +138
System.Data.Edm.Internal.EdmModelVisitor.VisitNamespaces(EdmModel model, IEnumerable`1 namespaces) +75
System.Data.Edm.Internal.EdmModelVisitor.VisitEdmModel(EdmModel item) +56
System.Data.Entity.ModelConfiguration.Configuration.EdmConventionDispatcher.VisitEdmModel(EdmModel item) +44
System.Data.Entity.ModelConfiguration.Configuration.ConventionsConfiguration.ApplyModel(EdmModel model) +126
System.Data.Entity.DbModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo) +125
System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection) +165
System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext) +61
System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input) +111
System.Data.Entity.Internal.LazyInternalContext.InitializeContext() +417
System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType) +18
System.Data.Entity.Internal.Linq.InternalSet`1.Initialize() +63
System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext() +15
System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider() +37
System.Linq.Queryable.FirstOrDefault(IQueryable`1 source, Expression`1 predicate) +63
Entities.User.GetCurrentPerson(String username, KmManagerDbContext context) in C:\Users\user\Documents\Visual Studio 2010\Projects\KmManager\Entities\User.cs:85
User.cs
public class User
{
public long Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Username { get; set; }
// Custom Propreties
public string FullName
{
get
{
return FirstName + " " + LastName;
}
}
public string LastNameFirst
{
get
{
return LastName + ", " + FirstName;
}
}
public static string TableName
{
get
{
return "Users";
}
}
public static User GetCurrentPerson(string username, KmManagerDbContext context)
{
try
{
// find the person who has the ad name = username
return context.Users.FirstOrDefault(p => p.Username.ToLower() == username.ToLower());
}
catch (Exception ex)
{
throw new ApplicationException("There was an error retrieving the user from the database.", ex);
}
}
}
UserConfiguration.cs
public UserConfiguration()
{
this.ToTable(User.TableName);
this.HasKey(x => x.Id);
this.Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
this.Property(x => x.FirstName).IsRequired();
this.Property(x => x.LastName).IsRequired();
this.Property(x => x.Username).IsRequired();
}
答案 0 :(得分:3)
如果有人担心答案......
我使用BaseEntity.cs
在我的POCO中分离了一些共性BaseEntity.cs
public class BaseEntity<T> where T : BaseEntity<T>
{
public long Id { get; set; }
public class Comparer : IEqualityComparer<T>
{
public bool Equals(T x, T y)
{
if (x.Id == y.Id)
{
return true;
}
return false;
}
public int GetHashCode(T obj)
{
return (int)obj.Id;
}
}
}
这导致配置具有奇怪的行为。我将所有POCO更改为之前的状态,一切都按预期工作。抱歉浪费时间。
用户POCO看起来像这样......
User.cs
public class User : BaseEntity<User>
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string Username { get; set; }
// Custom Propreties
public string FullName
{
get
{
return FirstName + " " + LastName;
}
}
public string LastNameFirst
{
get
{
return LastName + ", " + FirstName;
}
}
public static string TableName
{
get
{
return "Users";
}
}
public static User GetCurrentPerson(string username, KmManagerDbContext context)
{
try
{
// find the person who has the ad name = username
return context.Users.FirstOrDefault(p => p.Username.ToLower() == username.ToLower());
}
catch (Exception ex)
{
throw new ApplicationException("There was an error retrieving the user from the database.", ex);
}
}
}
答案 1 :(得分:3)
此错误不是查询问题,而是映射配置问题。似乎无论您在调用EF代码的查询是否会在类上找到重复的匹配属性时抛出错误。我猜它是在类公共setter中通过PropertyInfos循环。可能有重复的属性名称因为c#区分大小写所以'MyProperty','myproperty'都映射到同一列,或者在我的情况下因为自定义类索引器
对于类索引器: .net框架将索引器反映为properties with parameters。目前无法忽略EntityFramework代码第一个映射文件中的自定义索引器,因为lambda表达式无法表达这些特殊属性。由于这还不够,我的类有一个重载索引器(因此错误'序列包含多个匹配元素')
示例:
public decimal this[int month] {
get {
return _someArray[month];
}
set {
_someArray[month] = value;
}
}
public decimal this[int front, int month] {
get {
return _someArray2D[front - 1, month - 1];
}
set {
_someArray2D[front - 1, month - 1] = value;
}
}
很难跟踪。花了我一整天的时间来试图通过反复试验。
希望这有助于某人。
答案 2 :(得分:1)
不是答案,而是一个提示。基于Tekerik JustDecompile,该方法看起来像(EntityFramework.dll v4.2.0.0):
protected override EdmProperty MatchKeyProperty(EdmEntityType entityType, IEnumerable<EdmProperty> primitiveProperties)
{
return primitiveProperties.SingleOrDefault<EdmProperty>(delegate {
return string.Concat(entityType.Name, "Id").Equals(p.Name, stringComparison);
}) ?? primitiveProperties.SingleOrDefault<EdmProperty>(delegate {
return string.Concat(entityType.Name, "Id").Equals(p.Name, stringComparison);
});
}
似乎此函数试图找到您实体上的哪个属性是关键属性。期待用户 - &gt; UserId映射。我无法解释为什么SingleOrDefault被调用两次。