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《精通ASP.NET 4.0网络编程》实例测试出错，老师帮我看看吧！
本帖最后由 ～～敏 于 2012-2-13 22:42 编辑
（可以联系我QQ465506205, E-mail:pettyzhimin@163.com)
1.错误信息：
异常详细信息: System.Data.SqlClient.SqlException: 在与 SQL Server 建立连接时出现与网
络相关的或特定于实例的错误。未找到或无法访问服务器。请验证实例名称是否正确并且 SQL
Server 已配置为允许远程连接。 (provider: Named Pipes Provider, error: 40 - 无法打开到 SQL Server 的连接)
2.源错误:
行 96: where T : EntityObject
行 97: {
行 98: T entity = query.Where(predicate).FirstOrDefault();
行 99: query.MergeOption = MergeOption.NoTracking;
行 100: if (entity == null)
源代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Objects;
using System.Data;
using System.Data.Objects.DataClasses;
using System.Linq.Expressions;
using SJL.Common;
namespace SJL.Dal
{
/// <summary>
/// 实体框架工具
/// </summary>
/// <remarks>.NET Framework 4.0版</remarks>
internal static class EntityUtility
{
#region internal methods
#region most often used methods
internal static int add<TContext,TEntity>(TEntity entity)
where TContext:ObjectContext,new()
where TEntity:EntityObject
{
TContext context = new TContext();
int n= add(context, entity);
context.Dispose();
return n;
}
internal static int update<TContext, TEntity>(TEntity entity, params string[] excludeProperties)
where TContext : ObjectContext, new()
where TEntity : EntityObject
{
TContext context = new TContext();
int n = update(context, entity,excludeProperties);
context.Dispose();
return n;
}
internal static int delete<T>(ObjectQuery<T> query, Expression<Func<T, bool>> predicate)
where T : EntityObject
{ return delete(query, predicate, true); }
internal static T selectOne<T>(ObjectQuery<T> query, Expression<Func<T, bool>> predicate)
where T : EntityObject
{ return selectOne(query, predicate,true); }
//internal static List<T> selectMany<T, TSortKey>(ObjectQuery<T> query, Expression<Func<T, TSortKey>> sort,
//PageDataArgument page, params Expression<Func<T, bool>>[] predicate)
//where T : EntityObject
//{
// return selectMany(query, sort, false, page, predicate);
//}
//ObjectQuery<T> query, Expression<Func<T,TSortKey>> sort,bool sortDesc,
// PageDataArgument page,bool dispose=true,params Expression<Func<T,bool>>[] predicate
internal static List<T> selectMany<T, TSortKey>(ObjectQueryArgument<T, TSortKey> arg, params Expression<Func<T, bool>>[] predicate)
where T:EntityObject
{
return selectMany<T, TSortKey>(arg.query, arg.sort, arg.descending, arg.page, arg.disposeAfterQuery, predicate);
}
#endregion
#region do not use these methods unless you have strong reasons to do so
internal static int add<T>(ObjectContext context, T entity) where T:EntityObject
{
return add(context, entity.GetType().Name, entity);
}
internal static int update<T>(ObjectContext context, T entity, params string[] excludeProperties) where T : EntityObject
{
entity.EntityKey = context.CreateEntityKey(entity.GetType().Name, entity);
context.Attach(entity);
context.SetEntityStateToModified(entity,excludeProperties);
int n = context.SaveChanges();
detachEntity(context, entity);
return n;
}
internal static int delete<T>(ObjectQuery<T> query,Expression<Func<T, bool>> predicate,bool dispose)
where T:EntityObject
{
EntityObject entity = query.Where(predicate).FirstOrDefault();
if (entity == null)
return 0;
query.Context.DeleteObject(entity);
int n=query.Context.SaveChanges();
if (dispose)
query.Context.Dispose();
return n;
}
internal static T selectOne <T> (ObjectQuery<T> query, Expression<Func<T, bool>> predicate,bool dispose)
where T : EntityObject
{
T entity = query.Where(predicate).FirstOrDefault();
query.MergeOption = MergeOption.NoTracking;
if (entity == null)
{
if (dispose)
query.Context.Dispose();
return default(T);
}
detachAndRemoveEntityKey(query.Context,entity);
if (dispose)
query.Context.Dispose();
return entity;
}
internal static List<T> selectMany<T,TSortKey>(ObjectQuery<T> query, Expression<Func<T,TSortKey>> sort,bool sortDesc,
PageDataArgument page,bool dispose,params Expression<Func<T,bool>>[] predicate)
where T:EntityObject
{
query.MergeOption = MergeOption.NoTracking;
IQueryable<T> q = query;
for (int i = 0; i < predicate.Length; i++)
{
q = q.Where(predicate);
}
q=sortDesc?q.OrderByDescending(sort):q.OrderBy(sort);
if (page.refreshCount)
page.count = q.Count();
var list = q.Skip(page.pageIndex * page.pageSize).Take(page.pageSize).ToList();
detachEntity(query.Context, list);
if (dispose)
query.Context.Dispose();
return list;
}
//internal static List<T> selectMany<T, TSortKey>(ObjectQuery<T> query, Expression<Func<T, TSortKey>> sort,bool sortDesc,
//PageDataArgument page, params Expression<Func<T, bool>>[] predicate)
//where T : EntityObject
//{ return selectMany<T, TSortKey>(query, sort,sortDesc, page, true, predicate); }
#endregion
#endregion
#region AS private methods
//these methods should not be used outsied this class although they are interanl, which is a backward compatibility
internal static void detachEntity(ObjectContext context, EntityObject entity)
{
detachAndRemoveEntityKey(context, entity);
}
internal static void detachEntity<T>(ObjectContext context, List<T> list) where T : EntityObject
{
list.ForEach(item =>detachAndRemoveEntityKey(context, item));
}
#endregion
#region private methods
private static int add<T>(ObjectContext context, string entitySetName, T entity) where T : EntityObject
{
context.AddObject(entitySetName, entity);
int n = context.SaveChanges();
detachEntity(context, entity);
return n;
}
private static void detachAndRemoveEntityKey(ObjectContext context, EntityObject entity)
{
if(entity.EntityState!=EntityState.Detached)
context.Detach(entity);
entity.EntityKey = null;
}
#endregion
#region deleted code
/*
* Reversion History
* ----------------------------------------
* It is inconvinient to write where and order-by in this function. Rather, it would be better to write these with the LINQ.
* Use the LINQ to get a list, then use detachEntity method to detach the list from the context.
*
*/
// [Obsolete("Obsolete Method. Use LINQ on the context instead. (Sun Ji Lei)",true)]
//internal static List<T> getDetachedList<T>(ObjectQuery<T> query, System.Linq.Expressions.Expression<Func<T, bool>> ex) where T : EntityObject
//{
// var list = query.Where(ex).ToList();
// list.ForEach(o => { query.Context.Detach(o); o.EntityKey = null; });
// return list;
//}
// [Obsolete("Obsolete Method. Use LINQ on the context instead. (Sun Ji Lei)", true)]
//internal static List<T> getDetachedList<T,TKey>
// (ObjectQuery<T> query, System.Linq.Expressions.Expression<Func<T, bool>> ex, System.Linq.Expressions.Expression<Func<T, TKey>> sort)
// where T : EntityObject
//{
// var list = query.Where(ex).OrderBy(sort).ToList();
// list.ForEach(o => { query.Context.Detach(o); o.EntityKey = null; });
// return list;
//}
#endregion
}
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