从Access数据库删除按钮单击的特定记录

Question

我有一个包含9个字符的字符串，例如LON052012（来自伦敦23.05.2012。 - day.month.year。）。我想从Access中的表中删除所有城市的所有记录，其中所有城市都以该字符串的前三个字母开始，并具有这些月份和年份（05.2007。）。

这是函数：

private void button2_Click(object sender, EventArgs e) 
    { 
     if (textBox1.Text != "") 
     { 
      try 
      { 
       string sTown, s1, s2; 
       sTown = textBox1.Text.Substring(0, 3); 
       s1 = textBox1.Text.Substring(3, 2); 
       s2 = textBox1.Text.Substring(5); 

       string sDelete = "DELETE * FROM Country WHERE Town LIKE @p1 and month(TownDate) = @p2 and year(TownDate) = @p3"; 
       OleDbCommand komDelete = new OleDbCommand(sDelete, connection); 
       komDelete.Parameters.AddWithValue("@p1", sTown + "*"); 
       komDelete.Parameters.AddWithValue("@p2", s1); 
       komDelete.Parameters.AddWithValue("@p3", s2); 
       connection.Open(); 
       komDelete.ExecuteNonQuery(); 
       MessageBox.Show("Deleted"); 
      } 
      catch (Exception ex) 
      { 
       MessageBox.Show(ex.ToString()); 
      } 
      finally 
      { 
       connection.Close(); 
      } 
     } 
     else 
     { 
      MessageBox.Show("TextBox is empty!"); 
     } 
    } 

这是表国家的样子（CountryID，镇，TownDate）：

它总是说，该记录即使删除不是。

Answer 1

对于UPDATE，INSERT和DELETE语句，ExecuteNonQuery的返回值是受该命令影响的行数。

因此，修改代码为：

var n= komDelete.ExecuteNonQuery(); 
    if (n >0) 
    { 
      MessageBox.Show("Deleted"); 
    } 

编辑

查询的问题是：

• 参数的数据类型S1，S2，他们是字符串，并且他们 应该作为整数传递。
• 使用*，它应该是％（接入使用 ％，见我的评论）

所以，你必须修改代码为：

 var p1 = sTown + "%"; // not * 
     komDelete.Parameters.AddWithValue("@p1", p1); 
     var p2 = int.Parse(s1); //convert to numeric data type 
     var p3 = int.Parse(s2); 
     komDelete.Parameters.AddWithValue("@p2", p2); 
     komDelete.Parameters.AddWithValue("@p3", p3); 


     var n= komDelete.ExecuteNonQuery(); 
    if (n >0) 
    { 
      MessageBox.Show("Deleted"); 
    } 

我测试的代码访问2007年和2007年Office系统驱动程序：数据连接组件，它工作正常，并删除该行。

Answer 2

试试这个：

 if (textBox1.Text != "") 
    { 
     //retrieve data 
     string sTown, sMonth, sYear; 
     sTown = textBox1.Text.Substring(0, 3); 
     sMonth = textBox1.Text.Substring(3, 2); 
     sYear = textBox1.Text.Substring(5); 

     //validate input 
     bool valid_town = new Regex(@"[a-z]", RegexOptions.IgnoreCase).IsMatch(sTown) && new Regex(@"[^0-9]").IsMatch(sTown) && sTown.Length ==3; 
     bool valid_month = new Regex(@"[0][1-9]|[1][0-2]").IsMatch(sMonth) && new Regex(@"[^a-z]", RegexOptions.IgnoreCase).IsMatch(sMonth) && sMonth.Length ==2; 

     int year = 0; 
     bool isNum = int.TryParse(sYear,out year); 
     bool valid_year = new Regex(@"[^a-z]", RegexOptions.IgnoreCase).IsMatch(sYear) && sYear.Length == 4 && (isNum ? year > 1980 && year < 2100 : false); 



     string newLine = System.Environment.NewLine; 

     //if input valid 
     if (valid_town && valid_month && valid_year) 
     { 
      //create sql statements 
      string sWhere = String.Format("WHERE Town LIKE {0} and month(TownDate) = {1] and year(TownDate) = {2}", sTown,sMonth,sYear); 
      string sCount = String.Format("SELECT COUNT(*) FROM Country {0}", sWhere); 
      string sDelete = String.Format("DELETE * FROM Country {0}",sWhere); 

      //counts; to be deleted, actually deleted 
      int initialCount = 0; 
      int deletedCount = 0; 

      try 
      { 
       //create connection//NOTE: Using 'Use' statement will handle opening and closing. I dont know where you created your initial 'connection' object but it could cause you problems by haven a connection that is being used in multiple methods. 
       using (OleDbCommand connection = new OleDbCommand(ConnectionString)) 
       { 
        //get total rows to be affected 
        connection.CommandText = sCount; 
        initialCount = connection.ExecuteNonQuery(); 

        //delete rows and get delete count 
        connection.CommandText = sDelete; 
        deletedCount = connection.ExecuteNonQuery(); 
        //display message 
        MessageBox.Show(String.Format("Found {0} rows to delete. {1}Deleted {2} rows.", initialCount, newLine, deletedCount)); 

       } 
      } 
      catch (Exception ex) 
      { 
       MessageBox.Show(ex.ToString()); 
      } 
      finally 
      { 
       connection.Close(); 
      } 
     } 
     { 
      //else; input not valid 
      MessageBox.Show(String.Format("Failed validation of TextBox:{0}Country:{1}{2}Month{3}{4}Year{5}.", newLine, valid_town.ToString(), newLine, valid_month.ToString(), newLine, valid_year.ToString())); ; 

     } 
    } 
    else 
    { 
     MessageBox.Show("TextBox is empty!"); 
    } 

，你将需要添加此使用：

using System.Text.RegularExpressions; 

我没有得到一个机会来创建示例项目自己试试吧......