C# 单击按钮从Access数据库中删除特定记录
我有一个包含9个字符的字符串,例如LON052012(来自伦敦2012年5月23日-日.月.年)。我想从Access中的表中删除所有记录,其中所有城市都以该字符串的前三个字母开头,并具有这些月份和年份(05.2007.) 这就是功能:C# 单击按钮从Access数据库中删除特定记录,c#,sql,database,ms-access,ado.net,C#,Sql,Database,Ms Access,Ado.net,我有一个包含9个字符的字符串,例如LON052012(来自伦敦2012年5月23日-日.月.年)。我想从Access中的表中删除所有记录,其中所有城市都以该字符串的前三个字母开头,并具有这些月份和年份(05.2007.) 这就是功能: private void button2_Click(object sender, EventArgs e) { if (textBox1.Text != "") { try
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!");
}
}
这是表格Country的外观(CountryID、Town、TownDate):
它总是说即使记录没有被删除,也会被删除。对于UPDATE、INSERT和DELETE语句,ExecuteNonQuery的返回值是受命令影响的行数 因此,将代码修改为:
var n= komDelete.ExecuteNonQuery();
if (n >0 )
{
MessageBox.Show("Deleted");
}
编辑
查询中的问题有:
- 参数数据类型s1、s2,它们是字符串,并且 应作为整数传递李>
- 使用*并且应该是使用 %,见我的评论)
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");
}
我使用access 2007和2007 Office System Driver:Data Connectivity组件测试了该代码,它工作正常,并删除了该行 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!");
}
我没有机会创建示例项目来亲自尝试……在传递参数(例如komDelete.CommandText)后,您能否检查(并发布)您的sql语句。对于具有access的OLE连接,请使用%而不是*,查看我从那里尝试过的所有内容,但没有一个对我有效。当我从查询中删除月份(TownDate)和年份(TownDate)并仅按城市的前三个字母搜索时,它会从表中删除记录。因此,通过调试检查s1、s2是否为有效数字。使用trim从字符串中删除多余的空格。如果使用M.Hassan提供的确切逻辑,则可能会将数据库复制到项目的每个生成上的project\bin\debug文件夹中。要查看是否是这样,数据库将显示在解决方案资源管理器中。在解决方案资源管理器中选择数据库,然后选择属性。如果“复制到输出目录”设置为“始终复制”,则将其更改为“复制(如果更新)”。如果这不是一个解决方案,请验证您针对的是正确的数据库。
using System.Text.RegularExpressions;