无法使用 ADO.NET 建立到 SQL Server 的连接

Question

I'm trying to establish a connection to a local SQL server using this code:

dataGridView1.Visible = true;
        SqlConnection con = new SqlConnection();
        con.ConnectionString = @"Data Source=.;Initial Catalog=Form;Integrated Security=True";
        SqlCommand com = new SqlCommand("select * from Form", con);
        SqlDataAdapter sda = new SqlDataAdapter(com);
        dataGridView1.DataSource = sda;

But when I press the button in my form it doesn't show me the data! What am i doing wrong?

Answer 1

You need to open the connection with con.Open(); .

con.ConnectionString = @"Data Source=.;Initial Catalog=Form;Integrated   Security=True";
        SqlCommand com = new SqlCommand("select * from Form", con);
        con.Open();

Also you had a lot of other problems like you don't dispose your resource which can lead to memory leak and not closing your connection, also you are not filling your adapter. Here is optimal way to doing it.

using(SqlConnection con = new SqlConnection(@"Data Source=.;Initial Catalog=Form;Integrated Security=True";))
{          

    con.Open();
    SqlCommand com = new SqlCommand("select * from Form", con);
    using(SqlDataAdapter sda = new SqlDataAdapter(com));
    {
        DataTable resultTbl = new DataTable();
        sda.Fill(resultTbl);
        dataGridView1.DataSource = resultTbl;
        dataGridView1.DataBind();
    }
}

Answer 2

you need something like this

dataGridView1.Visible = true;
        SqlConnection con = new SqlConnection();
        con.ConnectionString = @"Data Source=.;Initial Catalog=Form;Integrated Security=True";
        con.Open()
        SqlCommand com = new SqlCommand("select * from Form", con);
        SqlDataAdapter sda = new SqlDataAdapter(com);
        DataTable dt=new DataTable();
        sda.Fill(dt);   

        dataGridView1.DataSource = dt;//set it to datatable
        dataGridView1.DataBind();