Gridview分頁問題

Question

我有一個問題讓我堆疊，我無法找到任何解決方案，非常需要你的幫助：其實我需要在員工表上進行一些搜索，就像我需要搜索所有女性或已經得到phd等職位，我做了這個查詢僱員表的函數，如果條件和這個搜索的結果進入一個gridview並允許爲真的問題是，只要我點擊下一步去到gridview中的其他頁面，它做了一個完整的回發，並再次綁定到gridview數據源，因爲我給gridview數據源下面的函數（DetailedSearch）與if cluases當它進入函數時，它開始閱讀與第一條件如果沒有去該特定條件，然後拋出異常未將對象引用設置爲對象的實例

這裏是我的代碼（這是它只是一個部分不完整的代碼）：

public DataTable DetailedSearch() 
    { 
     con.Open(); 
     SqlDataAdapter da=new SqlDataAdapter(); 


     if (FirstName != string.Empty) 
     { 
      if (FirstName != string.Empty && LastName != "--Letters--") 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'"+"and lastname like '"+LastName.ToString()+"%'", con); 
      } 
      else if(FirstName!=string.Empty && Gender!="{Please Select}") 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and gender='" + Gender.ToString() + "'", con); 

      } 
      else if(FirstName!=string.Empty && MaritalStatus!="{Please Select}") 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and maritalstatus='" + MaritalStatus.ToString() + "'", con); 
      } 
      else if(FirstName!=string.Empty && Qualification!="{Please Select}") 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and qualification='" + Qualification.ToString() + "'", con); 
      } 
      else if(FirstName!=string.Empty && GraduationDate!=DateTime.MinValue) 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and graduationdate='" + GraduationDate.ToString() + "'", con); 
      } 
      else if(FirstName!=string.Empty && Province!="{Please Select}") 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and province='" + Province.ToString() + "'", con); 
      } 
      else if(FirstName!=string.Empty && LastEmployer!=string.Empty) 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and lastemployer='" + LastEmployer.ToString() + "'", con); 
      } 
      else if(FirstName!=string.Empty && EnteredBy!="{Please Select}") 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and enteredby='" + EnteredBy.ToString() + "'", con); 
      } 
      else if (FirstName != string.Empty && DateEntered != DateTime.MinValue) 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'" + "and dateentered='" + DateEntered.ToString() + "'", con); 
      } 
      else 
      { 
       da = new SqlDataAdapter("select * from employee where firstname ='" + FirstName.ToString() + "'", con); 
      } 
     } 
     else if (LastName != "--Letters--") 
     { 
       if (LastName != "--Letters--" && Province != "{Please Select}") 
       { 
        da = new SqlDataAdapter("select * from employee where lastname like'" + LastName.ToString() + "%'" + "and province='" + Province.ToString() + "'", con); 
       } 
       else if (Gender != "{Please Select}" && LastName != "--Letters--") 
       { 
        da = new SqlDataAdapter("select * from employee where gender='" + Gender.ToString() + "'" + "and lastname like '" + LastName.ToString() + "%'", con); 
       } 
     DataTable dt = new DataTable(); 
     da.Fill(dt); 
     con.Close(); 
     return dt; 

    } 

請幫我該怎麼辦，是完全以空白，沒有邏輯來了我的腦海裏，我必須把if引導的從句的查詢可能是不一樣的基礎上，搜索，但如何讓gridview的分頁意識到了這一點:(提前

感謝

Answer 1

真的，也有可以改善的這麼多東西在那個代碼...

1. 你在做FirstName != string.Empty反覆，但你已經 在第一次測試它。
2. 你應該改變以單一if(!String.IsNullOrEmpty(FirstName))
3. 您應該使用sql parameters而不是字符串連接，因爲這避免了潛在的SQL注入
4. 你不應該傳遞字段的默認用戶界面，像「請選擇」 。在選擇默認值情況下 ，傳遞空或空值

雖然這不回答或具體問題，這是一個很好的指導 - 事實上，在情況下，你嘗試應用這些變化，它甚至可以解決你的問題在這個過程中