C# dataGridView shows no data

there are many posts about this, but no one helped me. Maybe i have just a logical problem or something like this. I'am a C# newbie.

So following problem. I have a dataGridView in Form1. When i click button1 Form6 appears, i give in a table name and fillDataGrid-mehtod runs in Form1. But. shows no Data the dataGradview just keeps empty with nothing in it.

Now the curios thing, if i place the Code from fillDataGrid-method in the button1 method every thing works fine.

Database (SQLite) connection works fine (not shown in the code example).

FORM1:

private void button1_Click(object sender, EventArgs e)
    {
        Form6 f6 = new Form6();
        f6.Show();


    }

    private void button3_Click(object sender, EventArgs e)
    {
        Form3 createTable = new Form3();
        createTable.Show();

    }


    public void fillDataGrid(String Eingabe)
    {


      String tabelle = Eingabe;

      String selectCommand = "select ID, VON, BIS, DAUER, KOMMENTAR from " + tabelle + ";";

      SQLiteDataAdapter dataAdapter = new SQLiteDataAdapter(selectCommand, sqlite_conn);
      DataSet ds = new DataSet();
      dataAdapter.Fill(ds);
      //dataGridView1.DataBindings.Clear();
      //dataGridView1.Columns.Clear(); 
      dataGridView1.AutoGenerateColumns = true;
      dataGridView1.DataSource = ds.Tables[0].DefaultView;






    }

FORM6:

 private void button1_Click(object sender, EventArgs e)
    {
        Form1 f1 = new Form1();
        String Eingabe = textBox5.Text;

        f1.fillDataGrid(Eingabe);
        Hide();



    }