求教，label.text 赋值无法显示

xchjian011 2012-03-21 03:24:34

求教各位大侠，下列代码中将数据库中总价列求和后赋值给 label2.text ，form框体上数值无法显示。求帮忙看看哪里有问题
private void label2_Click(object sender, EventArgs e)
{
OleDbConnection conn = new OleDbConnection();
String str = "./db1.mdb";
OleDbConnection OleDbcon = new OleDbConnection("Provider=Microsoft.jet.OLEDB.4.0;Data Source=" + str + ";User ID=admin;Password=;Jet OLEDB:Database Password=");
OleDbcon.Open();

OleDbCommand cmd = new OleDbCommand();
cmd.Connection = OleDbcon;
string s = label2.Text;
string select = String.Format("SELECT 总价 FROM sheet1 union all SELECT sum(总价) FROM sheet1", s);
cmd.CommandText = select;
OleDbDataReader reader = cmd.ExecuteReader();
reader.Read();
label2.Text = reader.GetString(0);
}

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xchjian011 2012-03-21

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dalmeeme
正解~~谢谢

dalmeeme 2012-03-21

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label2.Text = reader[0].ToString();

xchjian011 2012-03-21

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逐句运行的时候貌似没有涉及到这段代码

xchjian011 2012-03-21

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额...刚才不小心把label2属性改成隐藏了。。。怪不得运行成功

提示如下：
label2.Text = reader.GetString(0);
指定的转换无效

#blackheart 2012-03-21

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你确定if进去了吗？reader["列名"] as String;

xchjian011 2012-03-21

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应该是这个样子的么？依然是空白啊
private void label2_Click(object sender, EventArgs e)
{
OleDbConnection conn = new OleDbConnection();
String str = "./db1.mdb";
OleDbConnection OleDbcon = new OleDbConnection("Provider=Microsoft.jet.OLEDB.4.0;Data Source=" + str + ";User ID=admin;Password=;Jet OLEDB:Database Password=");
OleDbcon.Open();

OleDbCommand cmd = new OleDbCommand();
cmd.Connection = OleDbcon;
string s = label2.Text;
string select = String.Format("SELECT 总价 FROM sheet1 union all SELECT sum(总价) FROM sheet1", s);
cmd.CommandText = select;
OleDbDataReader reader = cmd.ExecuteReader();

if (reader.Read())
{
label2.Text = reader.GetString(0);
}

}