嘿Dreas，我也曾经为此苦恼过，但找到了一个非常优雅的解决方案。
你实际上需要使用DataContext.Attach(EntityToUpdate,OriginalEntity)方法。
有一些需要注意的地方...所以，阅读这些信息，它将会解释一切。
一旦你阅读完毕，随时可以向我提出任何问题。我基于那些信息编写了一个非常有用的EntitySaver类，如果需要，我们可以在你掌握要点后深入讨论你的类。
干杯！
编辑：
以下是我的完整类，如果你想尝试一下，这个类实际上可以自动处理更新和插入操作。如果你有任何问题，请告诉我。
实体保存器：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using QDAL.CoreContext;
using QDAL.CoreEntities;
using LinqExtension.CustomExtensions;
namespace QDAL
{
internal class DisconnectedEntitySaver
{
private QDataDataContext ContextForUpdate;
public DisconnectedEntitySaver() {
ContextForUpdate = Base.CreateDataContext();
}
public List<TEntityType> SaveEntities<TEntityType, TKeyType>(List<TEntityType> EntitiesToSave) {
string PKName;
PKName = Base.GetPrimaryKeyName(typeof(TEntityType), ContextForUpdate);
return SaveEntities<TEntityType, TKeyType>(EntitiesToSave, PKName);
}
public List<TEntityType> SaveEntities<TEntityType, TKeyType>(List<TEntityType> EntitiesToSave, string KeyFieldName)
{
List<TEntityType> EntitiesToPossiblyUpdate;
List<TEntityType> EntitiesToInsert;
List<TEntityType> HandledEntities = new List<TEntityType>();
bool TimeStampEntity;
Type ActualFieldType;
if (EntitiesToSave.Count > 0) {
TimeStampEntity = Base.EntityContainsTimeStamp(typeof(TEntityType), ContextForUpdate);
ActualFieldType = EntitiesToSave.FirstOrDefault().GetPropertyType(KeyFieldName);
if (ActualFieldType != typeof(TKeyType)) {
throw new Exception("The UniqueFieldType[" + typeof(TKeyType).Name + "] specified does not match the actual field Type[" + ActualFieldType.Name + "]");
}
if (ActualFieldType == typeof(string)) {
EntitiesToPossiblyUpdate = EntitiesToSave.Where(ent => string.IsNullOrEmpty(ent.GetPropertyValue<string>(KeyFieldName)) == false).ToList();
EntitiesToInsert = EntitiesToSave.Where(ent => string.IsNullOrEmpty(ent.GetPropertyValue<string>(KeyFieldName)) == true).ToList();
} else {
EntitiesToPossiblyUpdate = EntitiesToSave.Where(ent => EqualityComparer<TKeyType>.Default.Equals(ent.GetPropertyValue<TKeyType>(KeyFieldName), default(TKeyType)) == false).ToList();
EntitiesToInsert = EntitiesToSave.Where(ent => EqualityComparer<TKeyType>.Default.Equals(ent.GetPropertyValue<TKeyType>(KeyFieldName), default(TKeyType)) == true).ToList();
}
if (EntitiesToPossiblyUpdate.Count > 0) {
EntitiesToInsert.AddRange(ResolveUpdatesReturnInserts<TEntityType, TKeyType>(EntitiesToPossiblyUpdate, KeyFieldName));
HandledEntities.AddRange(EntitiesToPossiblyUpdate.Where(ent => EntitiesToInsert.Select(eti => eti.GetPropertyValue<TKeyType>(KeyFieldName)).Contains(ent.GetPropertyValue<TKeyType>(KeyFieldName)) == false));
}
if (EntitiesToInsert.Count > 0) {
ContextForUpdate.GetTable(typeof(TEntityType)).InsertAllOnSubmit(EntitiesToInsert);
HandledEntities.AddRange(EntitiesToInsert);
}
ContextForUpdate.SubmitChanges();
ContextForUpdate = null;
return HandledEntities;
} else {
return EntitiesToSave;
}
}
private List<TEntityType> ResolveUpdatesReturnInserts<TEntityType, TKeyType>(List<TEntityType> PossibleUpdates, string KeyFieldName)
{
QDataDataContext ContextForOrginalEntities;
List<TKeyType> EntityToSavePrimaryKeys;
List<TEntityType> EntitiesToInsert = new List<TEntityType>();
List<TEntityType> OriginalEntities;
TEntityType NewEntityToUpdate;
TEntityType OriginalEntity;
string TableName;
ContextForOrginalEntities = Base.CreateDataContext();
TableName = ContextForOrginalEntities.Mapping.GetTable(typeof(TEntityType)).TableName;
EntityToSavePrimaryKeys = (from ent in PossibleUpdates select ent.GetPropertyValue<TKeyType>(KeyFieldName)).ToList();
OriginalEntities = ContextForOrginalEntities.ExecuteQuery<TEntityType>("SELECT * FROM " + TableName + " WHERE " + KeyFieldName + " IN('" + string.Join("','", EntityToSavePrimaryKeys.Select(varobj => varobj.ToString().Trim()).ToArray()) + "')").ToList();
ContextForOrginalEntities = null;
foreach (TEntityType NewEntity in PossibleUpdates)
{
NewEntityToUpdate = NewEntity;
OriginalEntity = OriginalEntities.Where(ent => EqualityComparer<TKeyType>.Default.Equals(ent.GetPropertyValue<TKeyType>(KeyFieldName),NewEntityToUpdate.GetPropertyValue<TKeyType>(KeyFieldName)) == true).FirstOrDefault();
if (OriginalEntity == null)
{
EntitiesToInsert.Add(NewEntityToUpdate);
}
else
{
ContextForUpdate.GetTable(typeof(TEntityType)).Attach(CloneEntity<TEntityType>(NewEntityToUpdate), OriginalEntity);
}
}
return EntitiesToInsert;
}
protected TEntityType CloneEntity<TEntityType>(TEntityType EntityToClone)
{
var dcs = new System.Runtime.Serialization.DataContractSerializer(typeof(TEntityType));
using (var ms = new System.IO.MemoryStream())
{
dcs.WriteObject(ms, EntityToClone);
ms.Seek(0, System.IO.SeekOrigin.Begin);
return (TEntityType)dcs.ReadObject(ms);
}
}
}
}
你也需要这些辅助工具：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using QDAL.CoreContext;
using QDAL.CoreEntities;
using System.Configuration;
namespace QDAL
{
internal class Base
{
public Base() {
}
internal static QDataDataContext CreateDataContext() {
QDataDataContext newContext;
string ConnStr;
ConnStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
newContext = new QDataDataContext(ConnStr);
return newContext;
}
internal static string GetTableName(Type EntityType, QDataDataContext CurrentContext) {
return CurrentContext.Mapping.GetTable(EntityType).TableName;
}
internal static string GetPrimaryKeyName(Type EntityType, QDataDataContext CurrentContext) {
return (from m in CurrentContext.Mapping.MappingSource.GetModel(CurrentContext.GetType()).GetMetaType(EntityType).DataMembers where m.IsPrimaryKey == true select m.Name).FirstOrDefault();
}
internal static bool EntityContainsTimeStamp(Type EntityType, QDataDataContext CurrentContext) {
return (CurrentContext.Mapping.MappingSource.GetModel(CurrentContext.GetType()).GetMetaType(EntityType).DataMembers.Where(dm => dm.IsVersion == true).FirstOrDefault() != null);
}
}
}
这些扩展使反射更容易：
<System.Runtime.CompilerServices.Extension()> _
Public Function GetPropertyValue(Of ValueType)(ByVal Source As Object, ByVal PropertyName As String) As ValueType
Dim pInfo As System.Reflection.PropertyInfo
pInfo = Source.GetType.GetProperty(PropertyName)
If pInfo Is Nothing Then
Throw New Exception("Property " & PropertyName & " does not exists for object of type " & Source.GetType.Name)
Else
Return pInfo.GetValue(Source, Nothing)
End If
End Function
<System.Runtime.CompilerServices.Extension()> _
Public Function GetPropertyType(ByVal Source As Object, ByVal PropertyName As String) As Type
Dim pInfo As System.Reflection.PropertyInfo
pInfo = Source.GetType.GetProperty(PropertyName)
If pInfo Is Nothing Then
Throw New Exception("Property " & PropertyName & " does not exists for object of type " & Source.GetType.Name)
Else
Return pInfo.PropertyType
End If
End Function
