将INT作为null传递给搜索函数（使用LINQ的EF） [英] Passing INT as null into Search Function (EF using LINQ)

问题描述

我正在构建搜索功能（fname，lname，ChkNum，zip）。 INT中的ChkNum。我无法将NULL传递给INT，因为用户可能没有输入ChkNum进行搜索。

黑客代码在下面..它正在工作，但我确信有更好的方法。

 

 
  var  result = 
（ from  c < span style ="color：Blue;"> in  ctx.OfferOrdersDetails 
 其中 c.custFirstName.StartsWith（userFName）
 && c.custLastName.StartsWith（userLName）
  orderby  c.custLastName 
 选择 c 
）; 
 
  if （chkNum.HasValue）{
 result = result.Where（c => c.oOrderCheckNo == chkNum .value的）.OrderBy（C => c.custLastName）; 
} 
 
  if （！String.IsNullOrWhiteSpace（custZIP））
 result = result.Where（c = > c.custZIP.StartsWith（custZIP））。OrderBy（c => c.custLastName）; 
 
  return  result.ToList（）; 
} 
 

解决方案

LINQ在此阶段，实体不处理可为空的整数或IsNullOrWhiteSpace。您仍然可以在一行中编写查询，如下所示：

 var result = 
（来自c in ctx .OfferOrdersDetails 
其中c.custFirstName.StartsWith（userFName）
&& c.custLastName.StartsWith（userLName）
&&（！chkNum.HasValue || c.oOrderCheckNo = = chkNum.Value）
&&（custZIP == null || custZIP == String.Empty || c.custZIP.StartsWith（custZIP））
 orderby c.custLastName 
 select c 
）; 

 

~Rowan

I am building a search functions (fname,lname,ChkNum,zip) . ChkNum in INT. I can not pass a NULL into INT as the user might not enter a ChkNum for searching.

The hack code is below .. its working, but I am sure there is a better way.

 

var result =
 (from c in ctx.OfferOrdersDetails
  where c.custFirstName.StartsWith(userFName) 
  && c.custLastName.StartsWith(userLName)
  orderby c.custLastName
  select c
  );

if(chkNum.HasValue) {
  result = result.Where(c => c.oOrderCheckNo == chkNum.Value).OrderBy(c=>c.custLastName);
}

if (!String.IsNullOrWhiteSpace(custZIP))
  result = result.Where(c => c.custZIP.StartsWith(custZIP)).OrderBy(c=>c.custLastName);

return result.ToList();
}

解决方案

Hi,

LINQ to Entities doesn't handle nullable integers or IsNullOrWhiteSpace at this stage. You can still write the query in a single line as follows:

var result =
  (from c in ctx.OfferOrdersDetails
  where c.custFirstName.StartsWith(userFName)
  && c.custLastName.StartsWith(userLName)
  && (!chkNum.HasValue || c.oOrderCheckNo == chkNum.Value)
  && (custZIP == null || custZIP == String.Empty || c.custZIP.StartsWith(custZIP))
  orderby c.custLastName
  select c
  );

 

~Rowan

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