使用LINQ構建動態查詢

我將rebuilding this website php/mysql導入到asp.net中。我正在構建頁面標題中的主卡搜索表單。有一個文本輸入，多個下拉列表（全部指向不同的列）和一些條件搜索選項。使用LINQ構建動態查詢

對於mysql版本，我能夠使用條件來構建包含查詢的sting，然後執行它。

//MySql/PHP example 
$query = "SELECT * FROM cards WHERE "; 

    //Encounter_set 
if (isset($_GET['Encounter_Set']){ 
    $query.= "Encounter_Set=:Encounter_Set AND "; 
    $queryArray['Encounter_Set'] = $_GET['Encounter_Set']; 
} 

//radio statements 
switch ($_GET['radio']) { 
    case "All":  $query.= "(Title LIKE :terms OR Traits LIKE :terms OR Shadow_Text LIKE :terms OR Text LIKE :terms)";break; 
    case "Title": $query.= "(Title LIKE :terms)";break; 
    case "Traits": $query.= "(Traits LIKE :terms)";break; 
    case "Text": $query.= "(Shadow_Text LIKE :terms OR Text LIKE :terms)"; break; 
    default:  $query.= "(Title LIKE :terms OR Traits LIKE :terms OR Shadow_Text LIKE :terms OR Text LIKE :terms)"; 
} 

//Finally 
$result = $db_con->prepare($query);

我該怎麼去做這件事在LINQ？

來源

2012-12-15 Mason240

LINQ允許您撰寫查詢。 http://stackoverflow.com/questions/11194/conditional-linq-queries –

不會這inital聲明：'var logs =從登錄上下文.Logs選擇日誌;'將得到所有行表？從表中拉出每一行開始似乎效率不高。 – Mason240

不，linq是懶惰的，它不會執行查詢，直到您實際嘗試枚舉值 –

using (var context = new MyDbContext()) 
{ 
    IQueryable<Card> query = context.Cards; 
    if (!string.IsNullOrEmpty(Encounter_Set)) 
    { 
     query = query.Where(c => c.Encounter_Set == Encounter_Set); 
    } 
    switch (radio) 
    { 
     default: 
     case "All": 
      query = query.Where(c => c.Title.Contains(terms) 
       || c.Traits.Contains(terms) 
       || c.Shadow_Text.Contains(terms) 
       || c.Text.Contains(terms)); 
      break; 
     case "Title": 
      query = query.Where(c => c.Title.Contains(terms)); 
      break; 
     case "Traits": 
      query = query.Where(c => c.Traits.Contains(terms)); 
      break; 
     case "Text": 
      query = query.Where(c => c.Shadow_Text.Contains(terms) 
       || c.Text.Contains(terms)); 
      break; 
    } 
    // ... 
    return query.ToList(); // Execute the query 
}

來源

2012-12-15 17:27:13

使用LINQ構建動態查詢

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