ExecuteNonQuery：连接属性尚未初始化。 c锋利

Question

可能是我累了，但任何人都可以说出问题所在？

    SqlConnection conn = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename='c:\users\deltagare\documents\visual studio 2015\Projects\School\School\school.mdf';Integrated Security=True");
    private void Form1_Load(object sender, EventArgs e)
    {
        // TODO: This line of code loads data into the 'schoolDataSet.student' table. You can move, or remove it, as needed.
        //this.studentTableAdapter.Fill(this.schoolDataSet.student);

        conn.Open();
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;

        cmd.CommandText = "select * from student";

        cmd.ExecuteNonQuery();
        DataTable dt = new DataTable();
        student = new StudentController();
        SqlDataAdapter da = new SqlDataAdapter(cmd);

         da.Fill(dt);

        studentGridView.DataSource = dt;
        conn.Close();
    }

Answer 1

您必须要么使用SqlCommand(string,SqlConnection) 重载，要么设置SqlCommand.Connection 属性：

SqlCommand cmd = new SqlCommand("select * from student",conn);

或者

cmd.Connection=conn;

Answer 2

您必须在执行命令之前将连接分配给它：

cmd.Connection = conn