如果否则条件在linq查询中不起作用 [英] If else condition is not working in linq query

问题描述

我有这个代码：

  var  vr =（ 来自   context.GRI_Package 
  //   where（ISSTUDENT == true？s.StudentID == StudentUserID：s.TutorUserID == TutorUserID） 
  //   where（ISSTUDENT == true？s .StudentID == StudentUserID：（s.TutorUserID == TutorUserID&& s.StudentID == StudentUserID ）） 
 其中（ISSTUDENT ==  true ？（s.TutorUserID = =  0  || s.StudentID == StudentUserID）:( s.TutorUserID == TutorUserID&& s.StudentID == StudentUserID））
 < span class =code-comment> //  其中s.TutorUserID == TutorUserID&& s.StudentID == StudentUserID  
 选择  new  GetSessionpackageInfo 
 { 
 PackageID = s.PackageID，

}）。ToList（）;



vr。转储（）;



这里如果其他条件不是wokring有没有语法错误？

请帮帮我



我尝试了什么：



我试过这个条件

where（ISSTUDENT == true？（s.TutorUserID == 0 || s.StudentID == StudentUserID）:( s.TutorUserID == TutorUserID&& s.StudentID == StudentUserID））

解决方案

问题是您正在尝试在where子句中使用过程控制流逻辑。您需要了解WEHRE子句中的内容是布尔表达式而不是语句。



我将解释您之前的一个&更简单的尝试，你已经注释掉了。你有两个选择。对你来说更自然的可能就是在这样的C＃代码中做一个IF：

  var  query = context.GRI_Package; 
  if （ISSTUDENT）
 {
 query = query.Where（s = > ;  s.StudentID == StudentUserID）; 
} 
  else  
 {
 query = query.Where（s = >  s.TutorUserID == TutorUserID）; 
} 
  var  vr = query.Select（s = >   new  GetSessionpackageInfo {PackageID = s.PackageID}）。ToList（）; 

或者你可以拥有全部where子句但它必须是布尔表达而不是声明：

  var  vr =（ 来自 s   context.GRI_Package 
 其中（ISSTUDENT ==  true && s.StudentID == StudentUserID）
 ||（ISSTUDENT ==  false && s.TutorUserID == TutorUserID）
 选择  new  GetSessionpackageInfo 
 {
 PackageID = s.PackageID，
}）。ToList（）; 

I have this code :

var vr = (from s in context.GRI_Package
                              //where (ISSTUDENT == true ? s.StudentID == StudentUserID : s.TutorUserID == TutorUserID)
                              //where (ISSTUDENT == true ? s.StudentID == StudentUserID : (s.TutorUserID == TutorUserID && s.StudentID == StudentUserID))
                              where (ISSTUDENT == true ? (s.TutorUserID == 0 || s.StudentID == StudentUserID) : (s.TutorUserID == TutorUserID && s.StudentID == StudentUserID))
                              //where s.TutorUserID == TutorUserID && s.StudentID == StudentUserID
                              select new GetSessionpackageInfo
                              {
                                  PackageID = s.PackageID,

}).ToList();

vr.Dump();

here if else condition is not wokring is there any syntax mistake ?
please help me

What I have tried:

I tried this condition
where (ISSTUDENT == true ? (s.TutorUserID == 0 || s.StudentID == StudentUserID) : (s.TutorUserID == TutorUserID && s.StudentID == StudentUserID))

解决方案

The problem is that you are trying to use procedural control flow logic in the where clause. You need to understand that what's in the WEHRE clause is a boolean expression not a statement.

I will explain on one of your earlier & simpler attempts, which you have commented out. You have two options. More natural for you would be maybe do an IF in the C# code like this:

var query = context.GRI_Package;
if (ISSTUDENT)
{
    query = query.Where(s => s.StudentID == StudentUserID);
}
else
{
    query = query.Where(s => s.TutorUserID == TutorUserID);
}
var vr = query.Select(s => new GetSessionpackageInfo {PackageID = s.PackageID}).ToList();

Or you can have is all in the where clause but then it needs to be a boolean expresson and not a statement:

var vr = (from s in context.GRI_Package
          where (ISSTUDENT == true  && s.StudentID == StudentUserID) 
             || (ISSTUDENT == false && s.TutorUserID == TutorUserID)
          select new GetSessionpackageInfo
          {
              PackageID = s.PackageID,
          }).ToList();

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