Question

ExecuteReader:Connection属性尚未初始化，

private void textBox1_TextChanged(object sender, EventArgs e)
{
if (textBox1.Text.Trim() != null)
{
string str = "select * from VIP.[dbo].[商品目录]" + "where 货号=" + textBox1.Text.Trim().ToString();

cm = new SqlCommand();
cm.Connection = co;
cm.CommandText = str;
SqlDataReader reader = cm.ExecuteReader();
while (reader.Read())
{

this.textBox2.Text = reader[2].ToString().Trim();

}
co.Close();
reader.Close();

上面的程序 执行的时候 会出现 “ExecuteReader:Connection属性尚未初始化，”这是什么问题，怎么解决？

Answer 1

private void textBox1_TextChanged(object sender, EventArgs e)
{
string strconn="数据库的链接字符串";
SqlConnection co=new SqlConnection(strcon);
co.Open();
if (textBox1.Text.Trim() != null)
{
string str = "select * from VIP.[dbo].[商品目录]" + "where 货号=" + textBox1.Text.Trim().ToString();

cm = new SqlCommand(co.str);
SqlDataReader reader = cm.ExecuteReader();
while (reader.Read())
{

this.textBox2.Text = reader[2].ToString().Trim();

}
co.Close();
reader.Close();

Answer 2

con.Close();
con没写啊
给完整
SqlConnection
conn
=
new
SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);//数据库连接实例化
conn.Open();
SqlCommand
mycmd
=
new
SqlCommand();
mycmd.Connection
=
conn;
mycmd.CommandType
=
CommandType.Text;
SqlDataReader
sdr
=
mycmd.ExecuteReader();
while
(sdr.Read())
{
bzr
=
sdr[0].ToString();
shr
=
sdr[1].ToString();
qfr
=
sdr[2].ToString();
}
sdr.Close();

Answer 3

SqlCommand
cmd=new
SqlCommand("select
count
(*)from
productitem
where
pitemid='"+pitemid+"'");
这边漏了一个,con变量
SqlCommand
cmd=new
SqlCommand("select
count
(*)from
productitem
where
pitemid='"+pitemid+"'"
,
con);
//补上con就可以了

Answer 4

加上
SqlConnection
conn
=
new
SqlConnection(sql);
然后打开数据库
conn.Open();
然后语句运行完毕
conn.Close();

Answer 5

它的意思是就是说Connection属性没初始化啊，你的co初始化了没？