ado.net - 数据库未更新 ADO.Net

Question

我的程序中有一个客户类，在访问数据库中有一个客户表，我想按给定值更新数据库中的客户余额。 我写了所有看起来正确的语句，但不幸的是数据库没有受到影响。 这是我用来更新数据库的方法 提前致谢

public static bool UpdateCustomer(Customer customer)
{
   bool EditSucceeded = false;
   string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0; Data Source=C:\GarageProTuning.accdb;";

   using (OleDbConnection _con = new OleDbConnection(connectionString))
   {
      string commandText = "UPDATE Customer SET Balance=@Balance WHERE CustomerID=@CustomerID";

      using (OleDbCommand _cmd = new OleDbCommand(commandText, _con))
      {
         _cmd.Parameters.AddWithValue("@CustomerID", customer.CustomerID);
         _cmd.Parameters.AddWithValue("@Balance", customer.Balance);
         _con.Open();
         int rowsAffected = _cmd.ExecuteNonQuery();
         if (rowsAffected > 0)
            EditSucceeded = true;
         _con.Close();
      }
   }
   return EditSucceeded;
}

Answer 1

你有:

public static bool UpdateCustomer(Customer customer)
{
   bool EditSucceeded = false;
   string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0; Data Source=C:\GarageProTuning.accdb;";

   using (OleDbConnection _con = new OleDbConnection(connectionString))
   {
      string commandText = "UPDATE Customer SET Balance=@Balance WHERE CustomerID=@CustomerID";

      using (OleDbCommand _cmd = new OleDbCommand(commandText, _con))
      { 
         _cmd.Parameters.AddWithValue("@CustomerID", customer.CustomerID);
         _cmd.Parameters.AddWithValue("@Balance", customer.Balance);
         _con.Open();
         int rowsAffected = _cmd.ExecuteNonQuery();
         if (rowsAffected > 0)
            EditSucceeded = true;
         _con.Close();
      }
   }
   return EditSucceeded;
}

您需要的是:

public static bool UpdateCustomer(Customer customer)
{
   bool EditSucceeded = false;
   string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0; Data Source=C:\GarageProTuning.accdb;";

   using (OleDbConnection _con = new OleDbConnection(connectionString))
   {
      string commandText = "UPDATE Customer SET Balance=@Balance WHERE CustomerID=@CustomerID";

      using (OleDbCommand _cmd = new OleDbCommand(commandText, _con))
      { 
         _cmd.Parameters.AddWithValue("@Balance", customer.Balance);  // Explanation below
         _cmd.Parameters.AddWithValue("@CustomerID", customer.CustomerID);
         _con.Open();
         int rowsAffected = _cmd.ExecuteNonQuery();
         if (rowsAffected > 0)
            EditSucceeded = true;
         _con.Close();
      }
   }
   return EditSucceeded;
}

OleDbCommand.Parameters就如何添加/加工而言，它们是一种非常特殊的动物。从我链接的文档中:

Therefore, the order in which OleDbParameter objects are added to the OleDbParameterCollection must directly correspond to the position of the question mark placeholder for the parameter in the command text.

简而言之，您必须按照参数在命令文本中出现的顺序添加参数。