当然会出错,你的SqlDataReader实例没有调用read,应该如下:SqlCommand sqlcom=new SqlCommand("select max(ProductID) from 商品信息表",sqlcon); sqlcon.Open(); SqlDataReader dr=sqlcom.ExecuteReader(); int num=0; if(dr.Read()) num=dr.GetInt32(0); else MessageBox.Show("No data in DB");
sqlcon.Close();}
先要调用 SqlDataReader.read()方法. if (dr.read()) { int num=dr.GetInt32(0); }
sqlcon.Open();
SqlDataReader dr=sqlcom.ExecuteReader();
int num=0;
if(dr.Read())
num=dr.GetInt32(0);
else
MessageBox.Show("No data in DB");
sqlcon.Close();}
if (dr.read())
{
int num=dr.GetInt32(0);
}