C＃數據庫查詢錯誤信息？

我目前正在爲我在大學的第二個編程課上做最後的練習，並且在通過數據庫搜索特定員工姓名時遇到問題，如果用戶輸入的用戶名不在數據庫中，程序崩潰給出錯誤，而不是顯示我創建的錯誤消息。搜索C＃數據庫查詢錯誤信息？

方法：

public void searchNameDbMethod() 
    { 
     OleDbConnection Myconnection = null; 
     OleDbDataReader dbReader = null; 
     string selectionText = ""; 
     bool errorFlag = true; 

     do 
     { 
      string searchName = ""; 
      Console.Write("Search for Employee Name: "); 
      searchName = Console.ReadLine(); 
      searchName = searchName.ToUpper(); 
      Console.WriteLine("\n"); 

      Myconnection = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0; Data Source= payrolldb.accdb"); 

      Myconnection.Open(); 
      selectionText = "SELECT * FROM Table1;"; 
      OleDbCommand cmd = Myconnection.CreateCommand(); 
      cmd.CommandText = selectionText; 
      dbReader = cmd.ExecuteReader(); 

      if (dbReader.HasRows) 
      { 
       while (dbReader.Read()) 
       { 
        // since the query produces one column, the GetValue(0)   
        //must be set     
        // with multiple column queries, you have to know which 
        //column holds 
        // the value that you are looking for      
        //field 0 = ID 
        dbName = dbReader.GetValue(1).ToString();   //1 is field 1 of the db 
        if (dbName == searchName) 
        { 
         dbName = dbReader.GetValue(1).ToString();   //1 is field 1 of the db 
         dbID = dbReader.GetValue(2).ToString(); //2 is field 2 of the db 
         dbHourlyWage = dbReader.GetValue(3).ToString(); 
         dbDependents = dbReader.GetValue(4).ToString(); 

         Console.Clear(); 
         Console.ResetColor(); 
         Console.ForegroundColor = ConsoleColor.Green; 
         Console.WriteLine("*******************************************************"); 
         Console.WriteLine("**************** {0} *****************", date); 
         Console.WriteLine("*******************************************************"); 
         Console.WriteLine("Employee Name: ", dbName); 
         Console.WriteLine("Employee ID: {0}", dbID); 
         Console.WriteLine("Hourly Wage: {0}", dbHourlyWage); 
         Console.WriteLine("Number of Dependents: {0}", dbDependents); 
         Console.WriteLine("*******************************************************"); 
         Console.ResetColor(); 
         Console.Write("\n\n"); 

         errorFlag = false; 
        }//closes if    
       }// end of while 
      }// end of if 
      if (errorFlag == true) 
      { 
       Console.ResetColor(); 
       Console.ForegroundColor = ConsoleColor.Red; 
       Console.WriteLine("Name is not in our database!");//shows the data accumulated from above  
       Console.ResetColor(); 
      }//closes if 
      dbReader.Close(); 
      Myconnection.Close(); 
     }//close do 
     while (errorFlag == true); 
    }//closes searchNameDbMethod

的錯誤：http://puu.sh/4cPWU.png

請記住，我使用的Microsoft Access我的數據庫爲這個項目（不知道它的問題）。

我該如何做到這一點，以便如果在數據庫中找不到名稱，它將顯示我創建的錯誤消息，而不是在鏈接的圖像中顯示錯誤（崩潰程序）？

來源

2013-08-28 Meta

請參閱此鏈接http://social.msdn.microsoft.com/Forums/en-US/1d5c04c7-157f-4955-a14b-41d912d50a64/how-to-fix-error-the-microsoftaceoledb120-provider-未在本地機器上註冊 –

您安裝了哪種版本的訪問？ – Gonzix

@Gonzix Access 2010 – Meta

我想你應該在SQL-Where-Clause中搜索你的員工。

selectionText = "SELECT * FROM Table1 WHERE <EmployeeName> like @Name;";

然後給你的SQL查詢添加一個參數。

一般我會寫我的代碼是這樣的：

void searchNameDbMethod() 
{ 
    OleDbConnection Myconnection = null; 
    OleDbDataReader dbReader = null; 
    string selectionText = ""; 


    string searchName = ""; 
    Console.Write("Search for Employee Name: "); 
    searchName = Console.ReadLine(); 
    searchName = searchName.ToUpper(); 
    Console.WriteLine("\n"); 

    Myconnection = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0; Data Source= payrolldb.accdb"); 

    Myconnection.Open(); 
    selectionText = "SELECT * FROM Table1 WHERE Employee like @Name;"; 
    OleDbCommand cmd = Myconnection.CreateCommand(); 
    cmd.CommandText = selectionText; 

    cmd.Parameters.Add(new OleDbParameter() { ParameterName = "@Name", Value = searchName, DbType = System.Data.DbType.String }); 

    try 
    { 
     dbReader = cmd.ExecuteReader(CommandBehavior.CloseConnection); 

     while (dbReader.Read()) 
     { 
      // since the query produces one column, the GetValue(0)   
      //must be set     
      // with multiple column queries, you have to know which 
      //column holds 
      // the value that you are looking for      
      //field 0 = ID 
      string dbName = dbReader.GetValue(1).ToString();   //1 is field 1 of the db 
      if (dbName == searchName) 
      { 
       dbName = dbReader.GetValue(1).ToString();   //1 is field 1 of the db 
       string dbID = dbReader.GetValue(2).ToString(); //2 is field 2 of the db 
       string dbHourlyWage = dbReader.GetValue(3).ToString(); 
       string dbDependents = dbReader.GetValue(4).ToString(); 

       Console.Clear(); 
       Console.ResetColor(); 
       Console.ForegroundColor = ConsoleColor.Green; 
       Console.WriteLine("*******************************************************"); 
       Console.WriteLine("**************** {0} *****************", date); 
       Console.WriteLine("*******************************************************"); 
       Console.WriteLine("Employee Name: ", dbName); 
       Console.WriteLine("Employee ID: {0}", dbID); 
       Console.WriteLine("Hourly Wage: {0}", dbHourlyWage); 
       Console.WriteLine("Number of Dependents: {0}", dbDependents); 
       Console.WriteLine("*******************************************************"); 
       Console.ResetColor(); 
       Console.Write("\n\n"); 
      } 
     } 
    } 
    catch 
    { 
     if (dbReader != null) 
     { 
      dbReader.Close(); 
     } 
    } 
    finally 
    { 
     if (Myconnection != null) 
     { 
      Myconnection.Close(); 
     } 
    } 
}

只是一個例子，以提高您的解決方案。

來源

2013-08-28 06:49:03 BendEg

在這種情況下，我會在哪裏放置自定義錯誤消息「名稱不在我們的數據庫中！」？新名稱參數行也需要在查詢行之上（這種方式在使用之前聲明）。 – Meta

哦，我犯了一個錯誤，你不需要** if（dbName == searchName）** anmyore。但是你可以在你的while循環中做一個計數器並計算找到的僱員。 – BendEg

隨着您發佈的代碼，我得到以下錯誤http://puu.sh/4cR3b.png以前從未使用過這個東西，所以我不知道該怎麼做才能解決這個問題？你怎麼建議做這樣的事情呢？ *即時通訊對編程仍然很新穎，並不是100％熟悉很多東西* – Meta

我能夠基於一些由@BendEg

這裏提供的代碼來算起來我們的是我做過什麼：

public void searchNameDbMethod() 
    { 
     OleDbConnection Myconnection = null; 
     OleDbDataReader dbReader = null; 
     string selectionText = ""; 
     bool errorFlag = true; 

     do 
     { 
      string searchName = ""; 
      Console.Write("Search for Employee Name: "); 
      searchName = Console.ReadLine(); 
      searchName = searchName.ToUpper(); 
      Console.WriteLine("\n"); 

      Myconnection = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0; Data Source= payrolldb.accdb"); 

      Myconnection.Open(); 
      selectionText = "SELECT * FROM Table1 WHERE employee_name='" + searchName + "'"; 
      OleDbCommand cmd = Myconnection.CreateCommand(); 
      cmd.CommandText = selectionText; 
      dbReader = cmd.ExecuteReader(); 

      if (dbReader.HasRows) 
      { 
       while (dbReader.Read()) 
       { 
        // since the query produces one column, the GetValue(0)   
        //must be set     
        // with multiple column queries, you have to know which 
        //column holds 
        // the value that you are looking for      
        //field 0 = ID 
        dbName = dbReader.GetValue(1).ToString();   //1 is field 1 of the db 
        if (dbName == searchName) 
        { 
         dbName = dbReader.GetValue(1).ToString();   //1 is field 1 of the db 
         dbID = dbReader.GetValue(2).ToString(); //2 is field 2 of the db 
         dbHourlyWage = dbReader.GetValue(3).ToString(); 
         dbDependents = dbReader.GetValue(4).ToString(); 

         Console.Clear(); 
         Console.ResetColor(); 
         Console.ForegroundColor = ConsoleColor.Green; 
         Console.WriteLine("*******************************************************"); 
         Console.WriteLine("**************** {0} *****************", date); 
         Console.WriteLine("*******************************************************"); 
         Console.WriteLine("Employee Name: ", dbName); 
         Console.WriteLine("Employee ID: {0}", dbID); 
         Console.WriteLine("Hourly Wage: {0}", dbHourlyWage); 
         Console.WriteLine("Number of Dependents: {0}", dbDependents); 
         Console.WriteLine("*******************************************************"); 
         Console.ResetColor(); 
         Console.Write("\n\n"); 

         errorFlag = false; 
        }//closes if    
       }// end of while 
      }// end of if 
      else if (!dbReader.HasRows) 
      { 
       Console.ResetColor(); 
       Console.ForegroundColor = ConsoleColor.Red; 
       Console.WriteLine("Name is not in our database!");//shows the data accumulated from above  
       Console.ResetColor(); 
      }//closes if 
      dbReader.Close(); 
      Myconnection.Close(); 
     }//close do 
     while (errorFlag == true); 
    }//closes searchNameDbMethod

正如你可以看到我改變了我的詢問像他建議（但沒有額外的複雜的東西），並改變我的if（errorFlag == true）語句，否則如果（！dbReader.HasRows），它似乎像一個魅力工作！

來源

2013-08-28 07:37:04 Meta

C＃數據庫查詢錯誤信息？

回答

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