C#confirm表行已从数据库中删除

Question

我编写了一个方法,它将尝试根据主键id从db表中删除一行.我遇到的问题是try块总是返回"Success",即使记录已被删除/或它不存在.

public string delete_visit(int id)
        {
            string deleteResponse = null;
            string cnn = ConfigurationManager.ConnectionStrings[connname].ConnectionString;
            using (SqlConnection connection = new SqlConnection(cnn))
            {
                string SQL = string.Empty;
                SQL = "DELETE FROM [" + dbname + "].[dbo].[" + tbname + "]  WHERE VisitorNumber = @IDNumber ";

                using (SqlCommand command = new SqlCommand(SQL, connection))
                {
                    command.Parameters.Add("@IDNumber", SqlDbType.Int);
                    command.Parameters["@IDNumber"].Value = id;
                    try
                    {
                        connection.Open();
                        command.ExecuteNonQuery();

                        deleteResponse = "Success";

                    }
                    catch (Exception ex)
                    {
                        deleteResponse = "There was a problem deleting the visit from the database. Error message: " + ex.Message;
                    }
                }

            }

            return deleteResponse;
        }

我希望能够判断该行是否受到影响.我可以在SQL Server Management Studio中执行此操作,如下所示:

DELETE FROM Visits
WHERE VisitorNumber=88;
IF @@ROWCOUNT = 0
PRINT 'Warning: No rows were updated';

所以我想知道如何将@@ ROWCOUNT位插入到我的c#中,以便我可以判断该行是否已被删除？

谢谢

Answer 1

ExecuteNonQuery()返回一个int,表示受影响的行数.

所以:

int rowsAffected = command.ExecuteNonQuery();
if (rowsAffected == 0)
{
    deleteResponse = "No rows affected";
}

问题是这个数字可能会根据查询实际执行的内容而受到影响.执行触发器或调用存储过程可能会弄乱输出,从而更改受影响的行数.如果你真的必须,那么首先执行一个查询,在那里检查具有给定ID的记录是否存在.