C#操作access数据库问题
程序代码： using (OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OleDb.4.0;Data Source=E:\db\numcity.mdb"))
{
conn.Open();
using (OleDbCommand cmd = new OleDbCommand())
{
= "select * from numcity where id=1";
labnum.Text = Convert.ToString(cmd.ExecuteScalar());
}
提示：ExecuteScalar: Connection 属性尚未初始化。
为什么？如何解决？using (OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OleDb.4.0;Data Source=E:\db\numcity.mdb"))
{
conn.Open();
string sql = "select * from list where id=1";
using (OleDbCommand cmd = new OleDbCommand(sql,conn))
{
labnum.Text = Convert.ToString(cmd.ExecuteScalar());
}
}
这样就可以，和上面的有什么区别？我刚学 各位高手指点啊！
刚才试了下，把
conn.Open();
string sql = null;
using (OleDbCommand cmd = new OleDbCommand(sql,conn))
{
labnum.Text = Convert.ToString(cmd.ExecuteScalar());
}
这样就可以，为什么？怎么用才规范？
[ 本帖最后由 孤零落叶寒 于 2011-4-4 19:40 编辑 ]
