Question

ExecuteNonQuery: Connection 属性尚未初始化

namespace good
{
public partial class Form3 : Form
{
SqlConnection conn;
SqlCommand cmd;
SqlDataAdapter ada;
DataSet ds;
private void Form3_Load(object sender, EventArgs e)
{
string ConnectionString = "Data Source=SASE;Initial Catalog=PAS;User ID=KEY;Password=PS";
conn = new SqlConnection(ConnectionString);
conn.Open();
if (conn.State == ConnectionState.Open)
;
else
MessageBox.Show("数据库连接失败,请重试");
}
private void button1_Click(object sender, EventArgs e)
{
string name = textBox1.Text.Trim().ToString();
cmd = new SqlCommand("INSERT INTO usertable(username) VALUES"+name, conn);
cmd.ExecuteNonQuery();
}

}
最后一句会报错说属性尚未初始化，为什么啊T T

Answer 1

连接数据库不能这么写的，connection常Open的话，不但消耗资源，长时间占用数据库连接，而且容易导致错误。建议把创建connection和command写在一起，并且在执行完以后Close。修改好以后再试试。
还有Sql语句好像也有问题，感觉拼接出来以后不能执行。你可以在数据库里先执行看看

Answer 2

string ConnectionString = "Data Source=SASE;Initial Catalog=PAS;User ID=KEY;Password=PS";
SqlConnection conn= new SqlConnection(ConnectionString);
SqlCommand cmd;