linq to sql case query
-
22-07-2019 - |
質問
C#でlinq to sqlデータクエリ式を使用してクエリを作成すると問題が発生します。
最終的に私がやろうとしているのは、この擬似コード式に基づいています。
public IQueryable<CTest> searchRecords(string category, string searchString, DateTime startDate, DateTime endDate, int searchType, int searchType2)
{
//-Search All Records
//-From the information table
//-By the category column containing a specific search
//-Also by
// ~if both a startDate and endDate are entered (not (0000,00,00) OR null) then get records
// by this expression
// ~else then don't worry about this statement
//-Also by
// ~if a searchType is equal zero(0) then search for records from the
// search_type table equal to zero(0)
// ~if a searchType is equal one(1) then search for records from the
// search_type table equal to one(1)
// ~else then don't worry about this statement
//-Also by
// ~if a searchType2 is equal zero(0) then search for records from the
// search_type table equal to zero(0)
// ~if a searchType2 is equal one(1) then search for records from the
// search_type table equal to one(1)
// ~else then don't worry about this statement
//Here is my attempt at it
/*
var table = db.table1;
switch (category)
{
case "_category1":
var records =
from c in table
where c.column1.ToString().Contains(searchString)
select new CTest
{
test_id = c.id,
test_name = c.name,
test_number = c.number,
date = ((startDate != null) && (endDate != null)) ? ((c.test_date >= startDate) && (c.test_date <= endDate)) :
c.test_date),
test_type = (searchType == 0 ? (c.searchType = 0) :
searchType == 1 ? (c.searchType = 1) :
c.searchType),
test_type2 = (searchType2 == 0 ? (c.searchType2 = 0) :
searchType2 == 1 ? (c.searchType2 = 1) :
c.searchType2)
};
break;
default:
break;
}
*/
}
事前に感謝します。
解決
これは、LINQ構文よりも拡張メソッドの方が簡単です。
var records = context.Table
.Where( c => c.column1.Contains( searchString ) );
if (startDate != null && endDate != null)
{
records = records.Where( c => c.test_date >= startDate
&& c.test_date <= endDate );
}
...
これにより、LINQ式が構築されていきます。評価は、Count()やToList()など、選択を実行する必要がある拡張機能を実際に呼び出すか、結果の要素を列挙するまで遅延されます。
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