Few days ago, a developer posts a comment in my previous article about “Adding Dynamic Rows in ASP.Net GridView Control with TextBoxes” asking if how to implement the same functionality with DropDownList.

In this example, I will going to show on how to generate a Row in GridView with DropDownList when clicking a Button that is residing inside a GridView Footer and retain the Selected Items of the DropDownList on postbacks.

Here are the code blocks below:

ASPX Source:

<html xmlns="http://www.w3.org/1999/xhtml">

<head runat="server">

    <title>Untitled Page</title>

</head>

<body>

    <form id="form1" runat="server">

    <div>

    <asp:gridview ID="Gridview1" runat="server" ShowFooter="true" AutoGenerateColumns="false">

        <Columns>

        <asp:BoundField DataField="RowNumber" HeaderText="Row Number" />

        <asp:TemplateField HeaderText="Header 1">

            <ItemTemplate>

                <asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="true">

                <asp:ListItem Value="-1">Select</asp:ListItem>

                </asp:DropDownList>

            </ItemTemplate>

        </asp:TemplateField>

        <asp:TemplateField HeaderText="Header 2">

            <ItemTemplate>

                <asp:DropDownList ID="DropDownList2" runat="server" AppendDataBoundItems="true">

                <asp:ListItem Value="-1">Select</asp:ListItem>

                </asp:DropDownList>

            </ItemTemplate>

        </asp:TemplateField>

        <asp:TemplateField HeaderText="Header 3">

            <ItemTemplate>

                <asp:DropDownList ID="DropDownList3" runat="server" AppendDataBoundItems="true">

                <asp:ListItem Value="-1">Select</asp:ListItem>

                </asp:DropDownList>

            </ItemTemplate>

            <FooterStyle HorizontalAlign="Right" />

            <FooterTemplate>

             <asp:Button ID="ButtonAdd" runat="server" Text="Add New Row"

                    onclick="ButtonAdd_Click" />

            </FooterTemplate>

        </asp:TemplateField>

        </Columns>

        </asp:gridview>

    </div>

    </form>

</body>

</html>

 

In the above declaration, I have set up some Template Fields columns so that GridView will automatically generate a row of DropDownLists when a new row is being added.You will also notice that I have added a Button Control under the FooterTemplate at the last column in the GridView.

Note: Since we are added a Control in the GridView footer, then be sure to set ShowFooter to TRUE in the GridView.

CODE BEHIND:

In this example we are going to populate the DropDownLists on the fly. Note that I am using a dummy data and stored it in the ArrayList just for the simplicity of this demo. 

    private ArrayList GetDummyData()

    {

        ArrayList arr = new ArrayList();

        arr.Add(new ListItem("Item1", "1"));

        arr.Add(new ListItem("Item2", "2"));

        arr.Add(new ListItem("Item3", "3"));

        arr.Add(new ListItem("Item4", "4"));

        arr.Add(new ListItem("Item5", "5"));

        return arr;

    }

 

    private void FillDropDownList(DropDownList ddl)

    {

        ArrayList arr = GetDummyData();

        foreach (ListItem item in arr)

        {

            ddl.Items.Add(item);

        }

    }

 

    private void SetInitialRow()

    {

        DataTable dt = new DataTable();

        DataRow dr = null;

 

        //Define the Columns

        dt.Columns.Add(new DataColumn("RowNumber", typeof(string)));

        dt.Columns.Add(new DataColumn("Column1", typeof(string)));

        dt.Columns.Add(new DataColumn("Column2", typeof(string)));

        dt.Columns.Add(new DataColumn("Column3", typeof(string)));

 

        //Add a Dummy Data on Initial Load

        dr = dt.NewRow();

        dr["RowNumber"] = 1;

        dt.Rows.Add(dr);

 

        //Store the DataTable in ViewState

        ViewState["CurrentTable"] = dt;

        //Bind the DataTable to the Grid

        Gridview1.DataSource = dt;

        Gridview1.DataBind();

       

        //Extract and Fill the DropDownList with Data

        DropDownList ddl1 = (DropDownList)Gridview1.Rows[0].Cells[1].FindControl("DropDownList1");

        DropDownList ddl2 = (DropDownList)Gridview1.Rows[0].Cells[2].FindControl("DropDownList2");

        DropDownList ddl3 = (DropDownList)Gridview1.Rows[0].Cells[3].FindControl("DropDownList3");

 

        FillDropDownList(ddl1);

        FillDropDownList(ddl2);

        FillDropDownList(ddl3);

 

    }

    private void AddNewRowToGrid()

    {

 

        if (ViewState["CurrentTable"] != null)

        {

            DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];

            DataRow drCurrentRow = null;

 

            if (dtCurrentTable.Rows.Count > 0)

            {

                drCurrentRow = dtCurrentTable.NewRow();

                drCurrentRow["RowNumber"] = dtCurrentTable.Rows.Count + 1;

                //add new row to DataTable

                dtCurrentTable.Rows.Add(drCurrentRow);

                //Store the current data to ViewState

                ViewState["CurrentTable"] = dtCurrentTable;

 

                for (int i = 0 ; i < dtCurrentTable.Rows.Count - 1; i++)

                {

                    //extract the DropDownList Selected Items

                    DropDownList ddl1 = (DropDownList)Gridview1.Rows[i].Cells[1].FindControl("DropDownList1");

                    DropDownList ddl2 = (DropDownList)Gridview1.Rows[i].Cells[2].FindControl("DropDownList2");

                    DropDownList ddl3 = (DropDownList)Gridview1.Rows[i].Cells[3].FindControl("DropDownList3");

 

                    // Update the DataRow with the DDL Selected Items

                    dtCurrentTable.Rows[i]["Column1"] = ddl1.SelectedItem.Text;

                    dtCurrentTable.Rows[i]["Column2"] = ddl2.SelectedItem.Text;

                    dtCurrentTable.Rows[i]["Column3"] = ddl3.SelectedItem.Text;

 

                }

 

                //Rebind the Grid with the current data

                Gridview1.DataSource = dtCurrentTable;

                Gridview1.DataBind();

            }

        }

        else

        {

            Response.Write("ViewState is null");

        }

 

        //Set Previous Data on Postbacks

        SetPreviousData();

    }

 

    private void SetPreviousData()

    {

        int rowIndex = 0;

        if (ViewState["CurrentTable"] != null)

        {

            DataTable dt = (DataTable)ViewState["CurrentTable"];

            if (dt.Rows.Count > 0)

            {

                for (int i = 0; i < dt.Rows.Count; i++)

                {

                    //Set the Previous Selected Items on Each DropDownList on Postbacks

                    DropDownList ddl1 = (DropDownList)Gridview1.Rows[rowIndex].Cells[1].FindControl("DropDownList1");

                    DropDownList ddl2 = (DropDownList)Gridview1.Rows[rowIndex].Cells[2].FindControl("DropDownList2");

                    DropDownList ddl3 = (DropDownList)Gridview1.Rows[rowIndex].Cells[3].FindControl("DropDownList3");

 

                    //Fill the DropDownList with Data

                    FillDropDownList(ddl1);

                    FillDropDownList(ddl2);

                    FillDropDownList(ddl3);

 

                    if (i < dt.Rows.Count - 1)

                    {

                        ddl1.ClearSelection();

                        ddl1.Items.FindByText(dt.Rows[i]["Column1"].ToString()).Selected = true;

 

                        ddl2.ClearSelection();

                        ddl2.Items.FindByText(dt.Rows[i]["Column2"].ToString()).Selected = true;

 

                        ddl3.ClearSelection();

                        ddl3.Items.FindByText(dt.Rows[i]["Column3"].ToString()).Selected = true;

                    }

 

                    rowIndex++;

                }

            }

        }

    }

 

    protected void Page_Load(object sender, EventArgs e)

    {

        if (!Page.IsPostBack)

        {

            SetInitialRow();

        }

    }

    protected void ButtonAdd_Click(object sender, EventArgs e)

    {

        AddNewRowToGrid();

    }

 

Method Definitions:

 

GetDummyData()

A method that returns an ArrayList. Basically this method contains the dummy data for populating the DropDownList

FillDropDownList(DropDownList ddl)

A method that fills the DropDownList with the dummy data.

SetInitialRow()

A method that binds the GridView on initial load with a single row of data. The DataTable defined in this method is stored in ViewState so that it can be referenced anywhere in the codes when it postbacks. Basically this table will serve as the original DataSource for the GridView.

AddNewRowToGrid()

A method that adds a new row to the GridView when a Button is clicked and store the newly added row values in the Original Table that was defined in the SetInitialRow() method.

SetPreviousData()

A method that retains all the items that was selected from the DropDownList when it postbacks.


The output would look something like below when you run it on the browser:

On Initial Load:

After Adding some Rows:

 

That’s it! Hope you will find this example useful!