C# DataGridView doesn't show data on other form [duplicate]

问题

This question already has answers here:

How to access Form1 Function from Form2 without creating new Form(); (1 answer)

I would like to control Form1 from Form2 (2 answers)

Closed 2 years ago.

I have two Windows Forms (Form1 and Form2). Form1 has a button (openfrm2) and a datagridview (dataGridView1). Form2 has a textbox (sql_textbox) and a button (button1).

Clicking on openfrm2 opens Form2, then I'm writing an SQL query in sql_textbox to view a table in a Postgres database and clicking on button1 should show the result of the query in dataGridView1. But it doesn't.

Here is my code:

Form1:

public BindingSource bindingSource1 = new BindingSource();

private void openfrm2_Click(object sender, EventArgs e)
{
    Form2 frm2 = new Form2();
    frm2.Show();
}

Form2:

private void button1_Click(object sender, EventArgs e)
{
    Form1 frm1 = new Form1();
    frm1.bindingSource1.DataSource = query();
    frm1.dataGridView1.DataSource  = frm1.bindingSource1;
}

DataTable query()
{
    NpgsqlConnectionStringBuilder cnsb = new NpgsqlConnectionStringBuilder();
    cnsb.Database = "postgres";
    cnsb.Username = "postgres";
    cnsb.Password = "root";
    cnsb.Host     = "localhost";
    DataTable dt  = new DataTable();

    using (NpgsqlConnection cnn = new NpgsqlConnection(cnsb.ConnectionString))
    {
        cnn.Open();

        using (NpgsqlCommand cmd = new NpgsqlCommand(sql_textbox.Text, cnn))
        {
            NpgsqlDataAdapter da = new NpgsqlDataAdapter(sql_textbox.Text, cnn);
            da.Fill(dt);
        }
    }
    return dt;
}

I tried the solutions written at similar questions, but nothing works. If I add a datagridview to Form2, and add this

dataGridView2.DataSource = frm1.bindingSource1;

line to button1_Click it shows the data, but I need to display it on Form1.

How can I do it?

来源：https://stackoverflow.com/questions/50159119/c-sharp-datagridview-doesnt-show-data-on-other-form

标签

winforms

datagridview