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    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private OleDbDataAdapter da;
        private OleDbDataAdapter daa;
        private DataTable dt;
        private DataTable dtt;
        private BindingSource bs = new BindingSource();
        private BindingSource bss = new BindingSource();

        public void Form1_Load(object sender,EventArgs e)
        {
            Start(sender, e);
        }
        public void Start(object sender, EventArgs e)
        {
            string connStr = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=Akten.mdb;";
            OleDbConnection conn = new OleDbConnection(connStr);

            if (radioButton1.Checked == true)
            {
                string ab = "Akte1";
                    
                    string selStr = "SELECT LaufNr,Reihe,stock1,stock2,stock3,stock4 FROM Akte1";
                    OleDbCommand cmd = new OleDbCommand("SELECT *FROM Akte1", conn);
                    da = new OleDbDataAdapter(selStr, conn);
                    OleDbCommandBuilder cb = new OleDbCommandBuilder(da);
                    da.SelectCommand = new OleDbCommand(selStr, conn);
                    dt = new DataTable(ab);
                    conn.Open();
                    da.Fill(dt);
                    conn.Close();
                    bs.DataSource = dt;
                    textBox20.DataBindings.Add("Text", bindingSource1, "Reihe");
                    bindingSource1.DataSource = dt;
                    dataGridView1.DataSource = dt;
            }
            if (radioButton2.Checked == true)
            {
                string ab = "Akte2";

                    string selStr = "SELECT LaufNr,Reihe,stock1,stock2,stock3,stock4 FROM Akte2";
                    OleDbCommand cmd = new OleDbCommand("SELECT *FROM Akte2", conn);
                    daa = new OleDbDataAdapter(selStr, conn);
                    OleDbCommandBuilder cb = new OleDbCommandBuilder(daa);
                    daa.SelectCommand = new OleDbCommand(selStr, conn);
                    dtt = new DataTable(ab);
                    conn.Open();
                    daa.Fill(dtt);
                    conn.Close();
                    bss.DataSource = dtt;
                    textBox20.DataBindings.Add("Text", bindingSource2, "Reihe");
                    bindingSource2.DataSource = dtt;
                    dataGridView1.DataSource = dtt;
            }
        }					

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table = new DataTable();
adapter = new OleDbDataAdapter();
adapter.Connection = new OleDbConnection("...");
textBox20.DataBindings.Add("Text", "Reihe");					

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string source = radioButton1.Checked ? "Akte1" : "Akte2"; // riecht nach nicht ganz sauberem DB-Aufbau ;)
adapter.SelectCommand = new OleDbCommand("select * from " + source, connection);
table.Clear();
adapter.Fill(table);