大家帮我看看我的c#链接数据库哪块有错误呢，在线等哦

[gaoyanna]

这是写在buttonclick里面的，运行到数据库链接那块就发生错误，而且读不到数据
string area = this.comboBox1.SelectedValue.ToString();


string strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;";
strConnection += @"Data Source=|DataDirectory|db1.mdb";
//获取数据库表进行查询
OleDbConnection objConnection = new OleDbConnection(strConnection); //建立连接
objConnection.Open(); //打开连接
OleDbCommand sqlcmd = new OleDbCommand(@"select WEIGHT_F,WEIGHT_S from TB_02 where AREA = area and MAIL = '+韵达+'", objConnection); //sql语句
OleDbDataReader reader = sqlcmd.ExecuteReader(); //执行查询
float weight_f = new float();
float weight_s = new float();
if (reader.Read())
{ //这个read调用很重要！不写的话运行时将提示找不到数据
weight_f = (float)reader["WEIGHT_F"]; //取得字段的值
weight_s = (float)reader["WEIGHT_S"];
objConnection.Close();
reader.Close();

float total02;
if (float.Parse(tb) <= 1) { total02 = weight_f; }
else if (1 < float.Parse(tb) && float.Parse(tb) <= 4) { total02 = weight_f + 1; }
else { total02 = weight_f + 1 + (float.Parse(tb) - 4) * weight_s; }
textBox2.Text = Convert.ToString(total02);
}
else { MessageBox.Show("获取数据错误"); textBox2.Text = ""; }

[gaoyanna]

谢谢大家，可以都试了现在出现了 weight_f = (float)reader["WEIGHT_F"]; //取得字段的值
这个提示是：

[li365941471]

帮忙mark

[hitlcyu19]

[Quote=引用 5 楼 gaoyanna 的回复:]

谢谢大家，可以都试了现在出现了 weight_f = (float)reader["WEIGHT_F"]; //取得字段的值
这个提示是：
[/Quote]
呵呵

[Neil198]

"select WEIGHT_F,WEIGHT_S from TB_02 where AREA = '"+area+"' and MAIL = '韵达'"


结贴

[捷哥1999]

objConnection.Open(); //打开连接

是上面这一句出错吗？

修改一下连接字符串：
string strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;";
strConnection += @"Data Source=|DataDirectory|db1.mdb";

修改为
string strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;";
strConnection += @"Data Source=|DataDirectory|\db1.mdb";

[gsq_0912]

领教!!!

[gaoyanna]

[Quote=引用 1 楼 computerfox 的回复:]
objConnection.Open(); //打开连接

是上面这一句出错吗？

修改一下连接字符串：
string strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;";
strConnection += @"Data Source=|DataDirectory|db1.mdb";

修改为
string strConne……
[/Quote]

谢谢，是读取数据的时候出现错误了

[xk1126]

OleDbCommand sqlcmd = new OleDbCommand(@"select WEIGHT_F,WEIGHT_S from TB_02 where AREA = area and MAIL = '+韵达+'", objConnection); //sql语句
肯定是你的SQl语句
你用参数吧
string sql="select select WEIGHT_F,WEIGHT_S from TB_02 where AREA = area and MAIL = @MAIL"
SqlParameter ps = new SqlParameter("@MAIL",你的值);