如何缩短我的linq代码？
如何缩短我的linq代码？
提问于 2010-08-11 16:30:53
嗨；我试着运行我的代码。我的程序运行得更慢了。我需要给性能也写更少的代码在GetAliSpReqs()，GetMaintData();GetAccess....GET(...我怎样才能写出更有效的下面代码。它们太慢了，也没有用。例如，我尝试用GetAliSpReqs()编写少于1-2行的代码？我怎么能做到呢？请帮帮我。
public void LoadById(string SearchItem)
{
var myTechnicTasks = engTaskCtx.Tasks.Where(task => task.MyTechnicReference.StartsWith(SearchItem)).Select(task => new MyTask()
{
id = task.id,
MyTechnicReference = task.MyTechnicReference,
MPDReference = task.MPDReference,
tasktypeid = task.tasktypeid,
shortdesc = task.shortdesc,
interval = task.interval,
critical = task.critical,
mandatory = task.mandatory,
dupinsp = task.dupinsp,
dualsystemmaint = task.dualsystemmaint,
MPDSkill = task.MPDSkill,
MPDCrew = task.MPDCrew,
MPDAccessMH = task.MPDAccessMH,
MPDTotalMH = task.MPDTotalMH,
extratime = task.extratime,
Team = task.Team,
MaintData = EngGetCalculatedTaskField.GetMaintData(task.id),
AliSpReqs = EngGetCalculatedTaskField.GetAliSpReqs(task.id),
Access = EngGetCalculatedTaskField.GetAccess(task.id),
preperation = task.preperation,
longdesc = task.longdesc,
applnotes = task.applnotes
});
MyTechnicTaskList = myTechnicTasks.ToList();
}
public static class EngGetCalculatedTaskField
{
private static TaskMaintenanceDataDataContext engTaskCtx { get; set; }
public static string GetMaintData(int taskID)
{
try
{
using (TaskCardContext.TaskMaintenanceDataDataContext dc = new TaskCardContext.TaskMaintenanceDataDataContext())
{
string maintenanceData = String.Empty;
foreach (var item in dc.TaskRelations.Where(tableRaletions => tableRaletions.TaskId == taskID && tableRaletions.RelTypeId == 12))
{
maintenanceData += item.RefMaintenance.shortdesc + "; ";
}
return maintenanceData.Substring(0, maintenanceData.Length - 2);
}
}
catch
{
return String.Empty;
}
}
public static string GetAliSpReqs(int taskID)
{
#region Old
try
{
using (TaskCardContext.TaskMaintenanceDataDataContext dc = new TaskCardContext.TaskMaintenanceDataDataContext())
{
string aliSpReqs = String.Empty;
foreach (var item in dc.TaskRelations.Where(tableRaletions => tableRaletions.TaskId == taskID && tableRaletions.RelTypeId == 13))
{
aliSpReqs += item.RefAliSpReq.shortdesc + "; ";
}
return aliSpReqs.Substring(0, aliSpReqs.Length - 2);
}
}
catch
{
return String.Empty;
}
#endregion
}
public static string GetAccess(int taskID)
{
#region Old
try
{
using (TaskCardContext.TaskMaintenanceDataDataContext dc = new TaskCardContext.TaskMaintenanceDataDataContext())
{
string access = String.Empty;
foreach (var item in dc.TaskRelations.Where(tableRaletions => tableRaletions.TaskId == taskID && tableRaletions.RelTypeId == 15))
{
access += item.RefAccessPanel.shortdesc + "; ";
}
return access.Substring(0, access.Length - 2);
}
}
catch
{
return String.Empty;
}
#endregion
}
}回答 2
Stack Overflow用户
回答已采纳
发布于 2010-08-11 16:33:26
让我们以这段代码为例：
string aliSpReqs = String.Empty;
foreach (var item in dc.TaskRelations.Where(tableRaletions =>
tableRaletions.TaskId == taskID
&& tableRaletions.RelTypeId == 13))
{
aliSpReqs += item.RefAliSpReq.shortdesc + "; ";
}
return aliSpReqs.Substring(0, aliSpReqs.Length - 2);你在一个循环中连接字符串。馊主意。相反，尝试这样做(假设.NET 4)：
var query = c.TaskRelations.Where(r => r.TaskId == taskID
&& r.RelTypeId == 13))
.Select(r => r.RefAliSpReq.shortdesc);
return string.Join("; ", query);在.NET 3.5中，你需要使用下面的代码：
var query = c.TaskRelations.Where(r => r.TaskId == taskID
&& r.RelTypeId == 13))
.Select(r => r.RefAliSpReq.shortdesc);
return string.Join("; ", query.ToArray());诚然，我不能断定这是否是导致速度变慢的真正原因--但如果有很多字符串的话，很可能是这样的。
顺便说一句，这是一个糟糕的想法：
catch
{
return String.Empty;
}相反，捕获特定的异常-或者在大多数情况下，只是让异常传播到调用者。至少你应该记录这个异常，这样你就能知道哪里出了问题。
Stack Overflow用户
发布于 2010-08-11 16:45:21
您的所有函数都使用不同的参数调用同一段代码：
try
{
using (TaskCardContext.TaskMaintenanceDataDataContext dc = new TaskCardContext.TaskMaintenanceDataDataContext())
{
string aliSpReqs = String.Empty;
foreach (var item in dc.TaskRelations.Where(tableRaletions => tableRaletions.TaskId == taskID && tableRaletions.RelTypeId == 13))
{
aliSpReqs += item.RefAliSpReq.shortdesc + "; ";
}
return aliSpReqs.Substring(0, aliSpReqs.Length - 2);
}
}
catch
{
return String.Empty;
}所以让我们用它来做一个函数：
private static string GetData(int taskID, int typeID)
{
try
{
using (TaskCardContext.TaskMaintenanceDataDataContext dc = new TaskCardContext.TaskMaintenanceDataDataContext())
{
//This was taken from Jons answer!!
var query = c.TaskRelations.Where(r => r.TaskId == taskID
&& r.RelTypeId == typeID))
.Select(r => r.RefAliSpReq.shortdesc);
return string.Join("; ", query.ToArray());
}
}
catch
{
return String.Empty;
}
}现在，您可以从所有其他函数中调用此函数，如：
public static string GetMaintData(int taskID)
{
return GetData(taskID, 12);
}所以这会使你的代码变得更短。为了提高性能，你应该使用Jons answer并在最后进行字符串的连接，而不是在每一步都使用+=，因为这是非常糟糕的。
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原文链接：
https://stackoverflow.com/questions/3456638
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