Display ASP.Net GridView Row data in TextBox outside GridView

In order to retrieve data, user have to select a value from a dropdownlist (DropDownListTDRCode). Below I show you some snippets of my codes:

.aspx codes

<table>
    <tr class="box">
        <td class="gap"></td>
        <td class="lbl"><asp:Label ID="LabelTraderCode" runat="server" Text="Trader Code" CssClass="label"></asp:Label></td>
        <td class="inp"><asp:TextBox ID="TextBoxTDRCode" runat="server" CssClass="input"></asp:TextBox></td>
        <td class="inp"><asp:DropDownList ID="DropDownListTDRCode" runat="server" AutoPostBack="true" AppendDataBoundItems="true" CssClass="dropdown" OnSelectedIndexChanged="DropDownListTDRCode_SelectedIndexChanged"></asp:DropDownList></td>
 
        <td class="lbl"><asp:Label ID="LabelTraderName" runat="server" Text="Trader Name" CssClass="label"></asp:Label></td>
        <td class="inp"><asp:TextBox ID="TextBoxTDRName" runat="server" CssClass="input"></asp:TextBox></td>
        <td class="gap">
    </tr>
</table>

.aspx.cs:

//GLType
protected void GridViewSelection_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        DropDownList DropDownListGLType = (e.Row.FindControl("DropDownListGLType") as DropDownList);
        //DropDownListGLType.Items.Clear();
        DropDownListGLType.DataSource = dt;
        DropDownListGLType.DataTextField = "DESCR";
        DropDownListGLType.DataValueField = "PARA_CODE";
        DropDownListGLType.DataBind();
 
        DropDownListGLType.Items.Insert(0, DefaultItem);
 
        //ViewState["CurrentTable"] = dt;
    }
}
 
protected void DropDownListGLType_SelectedIndexChanged(object sender, EventArgs e)
{
    GridViewRow gvrow = (sender as DropDownList).NamingContainer as GridViewRow;
    rowindex = (gvrow as GridViewRow).RowIndex;
    ViewState["rowindex"] = rowindex;
    int passing = Convert.ToInt32(ViewState["rowindex"]);
    GridViewRow row2 = GridViewSelection.Rows[passing];
 
    string QueryCUR = "SELECT GL_ACCNO, ACC_GROUP, DESCR, seq_no FROM BOS_M_GL where (acc_group = 'BC' and seq_no in ('90', '100')) or (acc_group = 'P10' and seq_no = '1')";
    string QueryDEP = "SELECT GL_ACCNO, ACC_GROUP, descr, seq_no FROM BOS_M_GL where acc_group = 'BC' and seq_no = '120'";
    string QueryRET = "SELECT GL_ACCNO, ACC_GROUP, descr, seq_no FROM BOS_M_GL where acc_group = 'BC' and seq_no = '135'";
    string QueryEXP = "SELECT GL_ACCNO, ACC_GROUP, descr, seq_no FROM BOS_M_GL where acc_group = 'P63' and seq_no = '1'";
 
    OracleDataAdapter adapterCUR = new OracleDataAdapter(QueryCUR, con);
    OracleDataAdapter adapterDEP = new OracleDataAdapter(QueryDEP, con);
    OracleDataAdapter adapterRET = new OracleDataAdapter(QueryRET, con);
    OracleDataAdapter adapterEXP = new OracleDataAdapter(QueryEXP, con);
 
    dt.Columns.AddRange(new DataColumn[4] { new DataColumn("GL_ACCNO"), new DataColumn("DESCR"), new DataColumn("ACC_GROUP"), new DataColumn("SEQ_NO") });
 
    GridViewRow row = GridViewSelection.SelectedRow;
    DropDownList DropDownListGLType = sender as DropDownList;
 
    if (DropDownListGLType.SelectedValue == "CUR")
    {
        (row2.FindControl("TextBoxGLAccNo") as TextBox).Text = "";
        adapterCUR.Fill(ds, "BOS_M_GL");
    }
    else if (DropDownListGLType.SelectedValue == "DEP")
    {
        (row2.FindControl("TextBoxGLAccNo") as TextBox).Text = "";
        adapterDEP.Fill(ds, "BOS_M_GL");
    }
    else if (DropDownListGLType.SelectedValue == "RET")
    {
        (row2.FindControl("TextBoxGLAccNo") as TextBox).Text = "";
        adapterRET.Fill(ds, "BOS_M_GL");
    }
    else if (DropDownListGLType.SelectedValue == "EXP")
    {
        (row2.FindControl("TextBoxGLAccNo") as TextBox).Text = "";
        adapterEXP.Fill(ds, "BOS_M_GL");
    }
    else
    {
        (row2.FindControl("TextBoxGLAccNo") as TextBox).Text = "";
        GridView2.Visible = false;
        return;
    }
 
    if (ds.Tables.Contains("BOS_M_GL"))
    {
        DataView BMGContent = ds.Tables["BOS_M_GL"].DefaultView;
 
        if (BMGContent.Count > 0)
        {
            GridView2.Visible = true;
            GridView2.DataSource = BMGContent;
            GridView2.DataBind();
        }
        else
        {
            (row2.FindControl("TextBoxGLAccNo") as TextBox).Text = "";
            GridView2.Visible = false;
        }
    }
 
    GridView2.DataSource = ds;
    GridView2.DataBind();
}
 
protected void GridView2_SelectedIndexChanged(object sender, EventArgs e)
{
    PassingGLAccNo();
}
 
protected void PassingGLAccNo()
{
    int passing = Convert.ToInt32(ViewState["rowindex"]);
    GridViewRow row2 = GridViewSelection.Rows[passing];
    (row2.FindControl("TextBoxGLAccNo") as TextBox).Text = GridView2.SelectedRow.Cells[0].Text;
 
}
//GLType

Below is my save button which can be used when inserting and updating data.

//Retrieve Data
protected void DropDownTDRCode()
{
    string QueryTDRCode = "SELECT TDR_CODE FROM BOS_M_TRADER ORDER BY TDR_CODE";
 
    OracleDataAdapter AdapterTDRCode = new OracleDataAdapter(QueryTDRCode, con);
    DataTable dtTDRCode = new DataTable();
 
    AdapterTDRCode.Fill(dtTDRCode);
 
    DropDownListTDRCode.Items.Insert(0, DefaultItem);
 
    DropDownListTDRCode.DataSource = dtTDRCode;
    DropDownListTDRCode.DataTextField = "TDR_CODE";
    DropDownListTDRCode.DataValueField = "TDR_CODE";
    DropDownListTDRCode.DataBind();
}
 
protected void DropDownListTDRCode_SelectedIndexChanged(object sender, EventArgs e)
{
    con.Open();
 
    RetrieveData();
 
    con.Close();
}
 
protected void RetrieveData()
{
    RetrieveTradingInfo();
    RetrieveGLInfo();
}
 
protected void RetrieveLocalData()
{
    TextBoxTDRCode.Text = L_TDRCode;
    TextBoxTDRName.Text = L_TDRName;
     
    //GLInfo
    //DropDownListGLType.SelectedValue = L_GLType;
    //GLInfo
}
 
protected void RetrieveTradingInfo()
{
    string QueryDropDownList = "SELECT * FROM BOS_M_TRADER WHERE TDR_CODE = :TDR_CODE ORDER BY TDR_CODE";
 
    using (OracleCommand cmd = new OracleCommand(QueryDropDownList, con))
    {
        cmd.Parameters.Add("TDR_CODE", OracleDbType.Varchar2).Value = DropDownListTDRCode.SelectedValue;
 
        using (OracleDataAdapter adapter = new OracleDataAdapter(cmd))
        {
            adapter.Fill(dt);
 
            try
            {
                if (dt.Rows.Count > 0)
                {
                    L_TDRCode = dt.Rows[0]["TDR_CODE"].ToString();
                    L_TDRName = dt.Rows[0]["TDR_NAME"].ToString();
                     
                    //GLInfo
                    //L_GLType = dt.Rows[0]["GL_TYPE"].ToString();
                    //GLInfo
                }
                else
                {
                    L_TDRCode = "";
                    L_TDRName = "";
                }
                RetrieveLocalData();
            }
            catch (OracleException oracleEx)
            {
                LabelWarning.Text = "Oracle Error: " + oracleEx.Message;
            }
            catch (FormatException formatEx)
            {
                LabelWarning.Text = "Format Error: " + formatEx.Message;
            }
            catch (Exception ex)
            {
                LabelWarning.Text = "Error: " + ex.Message;
            }
            finally
            {
                if (string.IsNullOrEmpty(LabelWarning.Text))
                {
                    LabelWarning.Text = "Operation successful!";
                }
            }
        }
    }
}
 
protected void RetrieveGLInfo()
{
    string QueryGLType = "SELECT * FROM BOS_M_TRADER_GL WHERE TDR_CODE = :TDR_CODE";
 
    using (OracleCommand cmd = new OracleCommand(QueryGLType, con))
    {
        cmd.Parameters.Add("TDR_CODE", OracleDbType.Varchar2).Value = DropDownListTDRCode.SelectedValue;
 
        using (OracleDataAdapter adapter = new OracleDataAdapter(cmd))
        {
            adapter.Fill(dt);
 
            try
            {
                if (dt.Rows.Count > 0)
                {
 
                }
            }
            catch (OracleException oracleEx)
            {
                LabelWarning.Text = "Oracle Error: " + oracleEx.Message;
            }
            catch (FormatException formatEx)
            {
                LabelWarning.Text = "Format Error: " + formatEx.Message;
            }
            catch (Exception ex)
            {
                LabelWarning.Text = "Error: " + ex.Message;
            }
            finally
            {
                if (string.IsNullOrEmpty(LabelWarning.Text))
                {
                    LabelWarning.Text = "Operation successful!";
                }
            }
        }
 
    }
}
//Retrieve Data

I created 2 GriedViews. The first GriedView (GridViewSelection) stores DropDownListGLType where when user select a value, the second GridView (GridView2) will show up below GridViewSelection. Inside GridView2, user can select whatever row (each row has a GL_ACCNO). After selecting a row, the value of GL_ACCNO will appear inside a TextBoxGLAccNo which is located inside the GridViewSelection.

.aspx.cs codes:

<div class="folder-content">              
    <br />
    <div>
        <asp:GridView ID="GridViewSelection" runat="server" AutoGenerateColumns="False" OnRowDataBound="GridViewSelection_RowDataBound" Visible="true" ShowFooter="false" >
            <Columns>
                <asp:TemplateField HeaderText="GL Type">
                    <ItemTemplate>
                        <asp:DropDownList ID="DropDownListGLType" runat="server" AutoPostBack="true" AppendDataBoundItems="true" OnSelectedIndexChanged="DropDownListGLType_SelectedIndexChanged" ></asp:DropDownList>
                    </ItemTemplate>
                </asp:TemplateField>
 
                <asp:TemplateField HeaderText="GL Acc No">
                    <ItemTemplate>
                        <asp:TextBox ID="TextBoxGLAccNo" runat="server"></asp:TextBox>
                    </ItemTemplate>
                    <%--<FooterStyle HorizontalAlign="Right" />
                    <FooterTemplate>
                        <asp:Button ID="ButtonAddRow" runat="server" Text="Add another row" OnClick="ButtonAddRow_Click"  />
                    </FooterTemplate>--%>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
    </div>
 
    <br />
 
    <div>
        <asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False" OnSelectedIndexChanged="GridView2_SelectedIndexChanged">
            <Columns>
                <asp:BoundField DataField="GL_ACCNO" HeaderText="GL Acc No" SortExpression="GL_ACCNO" />
                <asp:BoundField DataField="DESCR" HeaderText="Description" SortExpression="DESCR" />
                <asp:BoundField DataField="ACC_GROUP" HeaderText="Acc Group" SortExpression="ACC_GROUP" />
                <asp:BoundField DataField="SEQ_NO" HeaderText="Seq No" SortExpression="SEQ_NO" />
                <asp:ButtonField ButtonType="Button" CommandName="Select" Text="Select" />
            </Columns>
        </asp:GridView>
    </div> 
</div>

protected void ButtonSave_Click(object sender, EventArgs e)
{
    con.Open();
 
    string QueryCheckExistingTDRCode = "SELECT COUNT(*) FROM BOS_M_TRADER WHERE TDR_CODE = :TDR_CODE";
 
    using (OracleCommand CheckExistingTDRCodeCmd = new OracleCommand(QueryCheckExistingTDRCode, con))
    {
        CheckExistingTDRCodeCmd.Parameters.Add("TDR_CODE", OracleDbType.Varchar2).Value = DropDownListTDRCode.SelectedValue;
 
        int count = Convert.ToInt32(CheckExistingTDRCodeCmd.ExecuteScalar());
 
        if (count == 0)
        {
            InsertData();
        }
        else
        {
            UpdateData();
        }
    }
 
    con.Close();
}
 
protected void InsertData()
{
    string QueryInsertNewData = "INSERT INTO BOS_M_TRADER (TDR_CODE, TDR_NAME) " +
                //GAP
                "VALUES (:TDR_CODE, :TDR_NAME)";
 
 
    using (OracleCommand InsertNewDataCmd = new OracleCommand(QueryInsertNewData, con))
    {
        using (OracleDataAdapter AdapterInsert = new OracleDataAdapter(InsertNewDataCmd))
        {
            AdapterInsert.Update(dt);
 
            try
            {
                InsertNewDataCmd.Parameters.Add("TDR_CODE", OracleDbType.Varchar2).Value = TextBoxTDRCode.Text;
                InsertNewDataCmd.Parameters.Add("TDR_NAME", OracleDbType.Varchar2).Value = TextBoxTDRName.Text;
                 
                InsertNewDataCmd.ExecuteNonQuery();
            }
            catch (OracleException oracleEx)
            {
                LabelWarning.Text = "Oracle Error: " + oracleEx.Message;
            }
            catch (FormatException formatEx)
            {
                LabelWarning.Text = "Format Error: " + formatEx.Message;
            }
            catch (Exception ex)
            {
                LabelWarning.Text = "Error: " + ex.Message;
            }
            finally
            {
                if (string.IsNullOrEmpty(LabelWarning.Text))
                {
                    LabelWarning.Text = "Operation successful!";
                }
            }
        }
    }
}
 
protected void UpdateData()
{
    string QueryUpdateData = "UPDATE BOS_M_TRADER SET TDR_CODE = :TDR_CODE, TDR_NAME = :TDR_NAME WHERE TDR_CODE = :TDR_CODE";
 
    using (OracleCommand UpdateCmd = new OracleCommand(QueryUpdateData, con))
    {
        using (OracleDataAdapter AdapterUpdate = new OracleDataAdapter(UpdateCmd))
        {
            AdapterUpdate.Update(dt);
 
            try
            {
                UpdateCmd.Parameters.Add("TDR_CODE", OracleDbType.Varchar2).Value = TextBoxTDRCode.Text;
                UpdateCmd.Parameters.Add("TDR_NAME", OracleDbType.Varchar2).Value = TextBoxTDRName.Text;
  
                UpdateCmd.ExecuteNonQuery();
            }
            catch (OracleException oracleEx)
            {
                LabelWarning.Text = "Oracle Error: " + oracleEx.Message;
            }
            catch (FormatException formatEx)
            {
                LabelWarning.Text = "Format Error: " + formatEx.Message;
            }
            catch (Exception ex)
            {
                LabelWarning.Text = "Error: " + ex.Message;
            }
            finally
            {
                if (string.IsNullOrEmpty(LabelWarning.Text))
                {
                    LabelWarning.Text = "Operation successful!";
                }
            }
        }
    }
}
//Save Data

How do I retrieve the data of DropDownListGLType and TextBoxGLAccNo from the my database and how do insert and update the data into my database also?