Lambda或Linq方法來搜索多個參數

Question

我有一個列表的對象和id喜歡用多個參數查詢列表，以減少搜索結果的搜索頁面。

 int SecLink = (!string.IsNullOrEmpty(Request.QueryString["Sector"])) ? Convert.ToInt32(Request.QueryString["Sector"]) : 0; 
     int LocLink = (!string.IsNullOrEmpty(Request.QueryString["Location"])) ? Convert.ToInt32(Request.QueryString["Location"]) : 0; 
     int IndLink = (!string.IsNullOrEmpty(Request.QueryString["Industry"])) ? Convert.ToInt32(Request.QueryString["Industry"]) : 0; 
     int VacLink = (!string.IsNullOrEmpty(Request.QueryString["Vacancy"])) ? Convert.ToInt32(Request.QueryString["Vacancy"]) : 0; 

     string keyword = Request.QueryString["SearchTerm"]; 

     var dx = new DataX(); 
     var lstJobs = dx.GetAllJobs().Where(x => x.SectorLink.Equals(SecLink) && x.LocationLink.Equals(LocLink) && x.IndustryLink.Equals(IndLink) && x.VacancyTypeLink.Equals(VacLink) && x.JobName.Contains(keyword)).ToList(); 

     if (lstJobs.Count > 0) 
     { 
      uiRptSearchJobs.DataSource = lstJobs; 
      uiRptSearchJobs.DataBind(); 

      uiLitSearchResults.Text = string.Format("<h4>Search result found {0} matches</h4>", lstJobs.Count); 
     } 

由於沒有從上一頁中選擇搜索參數，所以搜索參數可能爲'0'，所以結果應該反映他的。

這是查詢字符串IM傳：

Default.aspx?section=search&Sector=4&Location=0&Industry=0&Vacancy=0&SearchTerm=

，但你可以看到他們的查詢字符串將與哪些用戶從以前的頁面選擇更改。

Answer 1

如果我理解正確，如果參數的值爲0，您不想過濾？如果是這樣，兩種解決方案：

1. 檢查的參數是你的條件等於0：

   var lstJobs = dx.GetAllJobs().Where(x => 
       (SecLink == 0 || x.SectorLink.Equals(SecLink)) 
       && (LocLink == 0 || x.LocationLink.Equals(LocLink)) 
       && (IndLink == 0 || x.IndustryLink.Equals(IndLink)) 
       && (VacLink == 0 || x.VacancyTypeLink.Equals(VacLink)) 
       && x.JobName.Contains(keyword)).ToList(); 
   

2. LINQ的善良，動態構造查詢：

   var query = dx.GetAllJobs().Where(x => x.JobName.Contains(keyword)); 
   
       if (SecLink != 0) 
       { 
        query = query.Where(x => x.SectorLink.Equals(SecLink)); 
       } 
   
       if (LocLink != 0) 
       { 
        query = query.Where(x => x.LocationLink.Equals(LocLink)); 
       } 
   
       if (IndLink != 0) 
       { 
        query = query.Where(x => x.IndustryLink.Equals(IndLink)); 
       } 
   
       if (VacLink != 0) 
       { 
        query = query.Where(x => x.VacancyTypeLink.Equals(VacLink)); 
       } 
   
       var lstJobs = query.ToList(); 
   

Answer 2

一種選擇是有條件執行Where條款：

如果搜索術語應當AND組合在一起：

var lstJobs = dx.GetAllJobs(); 

if (SecLink > 0) 
    lstJobs = lstJobs.Where(x => x.SectorLink.Equals(SecLink)) 

if (LocLink > 0) 
    lstJobs = lstJobs.Where(x => x.LocationLink.Equals(LocLink)) 

if (IndLink > 0) 
    lstJobs = lstJobs.Where(x => x.IndustryLink.Equals(IndLink)) 

if (VacLink > 0) 
    lstJobs = lstJobs.Where(x => x.VacationLink.Equals(VacLink)) 

// Performance does not suffer because the query will 
// not get evaluated until it's required. For example, 
// here we call .ToList, which forces the query to be evaluated. 
var result = lstJobs.ToList(); 

但是，你清楚你所需要的搜索字詞OR連起來。在這種情況下：

var lstJobs = dx.GetAllJobs().Where(x => x.JobName.Contains(keyword)); 

if (SecLink > 0) 
    lstJobs = lstJobs.Union(
     dx.GetAllJobs().Where(x => x.SectorLink.Equals(SecLink)) 

if (LocLink > 0) 
    lstJobs = lstJobs.Union(
     dx.GetAllJobs().Where(x => x.LocationLink.Equals(LocLink)) 

etc...