Dynamically adding and deleting rows from ASP.NET GridView

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Introduction 

This article talks about a small project that presents the idea of having a GridView which facilitates the addition and removal of rows dynamically at run time.

Background

There are many times when we need the user to enter some data but we are not sure about the amount of data. For instance, we need to have an application that takes the student details from a faculty member (possibility at the time of admission). We can design this page in two ways: either we take data of one student at a time or we allow the user to enter data of multiple users in a single go. Also we can let the user choose the number of records he want to enter.

Now to accomplish this, we design the page in such a way that the user will have the possibility of adding new rows dynamically and then entering the data. How we can do that will be the focus of the rest of the article.

Using the code

Let us first design the layout for taking a single record from the user.

This design has been achieved by having the template fields in the Gridview in the following manner.

<asp:GridView ID="grvStudentDetails" runat="server" 
                ShowFooter="True" AutoGenerateColumns="False"
                CellPadding="4" ForeColor="#333333" 
                GridLines="None" OnRowDeleting="grvStudentDetails_RowDeleting">
    <Columns>
        <asp:BoundField DataField="RowNumber" HeaderText="SNo" />
        <asp:TemplateField HeaderText="Student Name">
            <ItemTemplate>
                <asp:TextBox ID="txtName" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Student Age">
            <ItemTemplate>
                <asp:TextBox ID="txtAge" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Student Address">
            <ItemTemplate>
                <asp:TextBox ID="txtAddress" runat="server" 
                   Height="55px" TextMode="MultiLine"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Gender">
            <ItemTemplate>
                <asp:RadioButtonList ID="RBLGender" 
                           runat="server" RepeatDirection="Horizontal">
                    <asp:ListItem Value="M">Male</asp:ListItem>
                    <asp:ListItem Value="F">Female</asp:ListItem>
                </asp:RadioButtonList>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Qualification">
            <ItemTemplate>
                <asp:DropDownList ID="drpQualification" runat="server">
                    <asp:ListItem Value="G">Graduate</asp:ListItem>
                    <asp:ListItem Value="P">Post Graduate</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>
        <asp:CommandField ShowDeleteButton="True" />
    </Columns>
    <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
    <RowStyle BackColor="#EFF3FB" />
    <EditRowStyle BackColor="#2461BF" />
    <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
    <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
    <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
    <AlternatingRowStyle BackColor="White" />
</asp:GridView>

The basic idea here is that from the code-behind if we dynamically change the DataSource of this GridView the GridView will change accordingly. So what we will do is that we will have a single row exposed as default and then keep adding rows in the GridView whenever the user requests to add a new row. For that we will simply keep adding empty data items to the GridView data source resulting in the GridView getting changed dynamically.

Let us see the code to have a default single row:

private void FirstGridViewRow()
{
    DataTable dt = new DataTable();
    DataRow dr = null;
    dt.Columns.Add(new DataColumn("RowNumber", typeof(string)));
    dt.Columns.Add(new DataColumn("Col1", typeof(string)));
    dt.Columns.Add(new DataColumn("Col2", typeof(string)));
    dt.Columns.Add(new DataColumn("Col3", typeof(string)));
    dt.Columns.Add(new DataColumn("Col4", typeof(string)));
    dt.Columns.Add(new DataColumn("Col5", typeof(string)));
    dr = dt.NewRow();
    dr["RowNumber"] = 1;
    dr["Col1"] = string.Empty;
    dr["Col2"] = string.Empty;
    dr["Col3"] = string.Empty;
    dr["Col4"] = string.Empty;
    dr["Col5"] = string.Empty;
    dt.Rows.Add(dr);

    ViewState["CurrentTable"] = dt;

    grvStudentDetails.DataSource = dt;
    grvStudentDetails.DataBind();
}

The important thing to note in the above code is the use of the view state. The ViewState has been kept to facilitate the dynamic addition and deletion of rows functionality. Since we need to preserve the data of rows other than the row being added or deleted we need some place to keep this data. We choose ViewState for that.

Now whenever the user chooses to add a new row we need to do two things: first we need to add the new row in the grid and secondly we need to set the data entered in the already added rows.

So to add a new row to the GridView:

private void AddNewRow()
{
    int rowIndex = 0;

    if (ViewState["CurrentTable"] != null)
    {
        DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
        DataRow drCurrentRow = null;
        if (dtCurrentTable.Rows.Count > 0)
        {
            for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
            {
                TextBox TextBoxName = 
                  (TextBox)grvStudentDetails.Rows[rowIndex].Cells[1].FindControl("txtName");
                TextBox TextBoxAge = 
                  (TextBox)grvStudentDetails.Rows[rowIndex].Cells[2].FindControl("txtAge");
                TextBox TextBoxAddress = 
                  (TextBox)grvStudentDetails.Rows[rowIndex].Cells[3].FindControl("txtAddress");
                RadioButtonList RBLGender = 
                  (RadioButtonList)grvStudentDetails.Rows[rowIndex].Cells[4].FindControl("RBLGender");
                DropDownList DrpQualification = 
                  (DropDownList)grvStudentDetails.Rows[rowIndex].Cells[5].FindControl("drpQualification");
                drCurrentRow = dtCurrentTable.NewRow();
                drCurrentRow["RowNumber"] = i + 1;

                dtCurrentTable.Rows[i - 1]["Col1"] = TextBoxName.Text;
                dtCurrentTable.Rows[i - 1]["Col2"] = TextBoxAge.Text;
                dtCurrentTable.Rows[i - 1]["Col3"] = TextBoxAddress.Text;
                dtCurrentTable.Rows[i - 1]["Col4"] = RBLGender.SelectedValue;
                dtCurrentTable.Rows[i - 1]["Col5"] = DrpQualification.SelectedValue;
                rowIndex++;
            }
            dtCurrentTable.Rows.Add(drCurrentRow);
            ViewState["CurrentTable"] = dtCurrentTable;

            grvStudentDetails.DataSource = dtCurrentTable;
            grvStudentDetails.DataBind();
        }
    }
    else
    {
        Response.Write("ViewState is null");
    }
    SetPreviousData();
}

And to set the previoduly entered data:

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++)
            {
                TextBox TextBoxName = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[1].FindControl("txtName");
                TextBox TextBoxAge = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[2].FindControl("txtAge");
                TextBox TextBoxAddress = 
                  (TextBox)grvStudentDetails.Rows[rowIndex].Cells[3].FindControl("txtAddress");
                RadioButtonList RBLGender = 
                  (RadioButtonList)grvStudentDetails.Rows[rowIndex].Cells[4].FindControl("RBLGender");
                DropDownList DrpQualification = 
                  (DropDownList)grvStudentDetails.Rows[rowIndex].Cells[5].FindControl("drpQualification");

                TextBoxName.Text = dt.Rows[i]["Col1"].ToString();
                TextBoxAge.Text = dt.Rows[i]["Col2"].ToString();
                TextBoxAddress.Text = dt.Rows[i]["Col3"].ToString();
                RBLGender.SelectedValue = dt.Rows[i]["Col4"].ToString();
                DrpQualification.SelectedValue = dt.Rows[i]["Col5"].ToString();
                rowIndex++;
            }
        }
    }
}

Similar stuff needs to be done when the user chooses to delete the row. We need to delete the row the user selected and then we need to set the data of the previous rows.

To delete the row selected

protected void grvStudentDetails_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
    SetRowData();
    if (ViewState["CurrentTable"] != null)
    {
        DataTable dt = (DataTable)ViewState["CurrentTable"];
        DataRow drCurrentRow = null;
        int rowIndex = Convert.ToInt32(e.RowIndex);
        if (dt.Rows.Count > 1)
        {   
            dt.Rows.Remove(dt.Rows[rowIndex]);
            drCurrentRow = dt.NewRow();
            ViewState["CurrentTable"] = dt;
            grvStudentDetails.DataSource = dt;
            grvStudentDetails.DataBind();

            for (int i = 0; i < grvStudentDetails.Rows.Count - 1; i++)
            {
                grvStudentDetails.Rows[i].Cells[0].Text = Convert.ToString(i + 1);
            }
            SetPreviousData();
        }
    }
}

And then to reset the data in other rows

private void SetRowData()
{
    int rowIndex = 0;

    if (ViewState["CurrentTable"] != null)
    {
        DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
        DataRow drCurrentRow = null;
        if (dtCurrentTable.Rows.Count > 0)
        {
            for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
            {
                TextBox TextBoxName = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[1].FindControl("txtName");
                TextBox TextBoxAge = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[2].FindControl("txtAge");
                TextBox TextBoxAddress = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[3].FindControl("txtAddress");
                RadioButtonList RBLGender = 
                  (RadioButtonList)grvStudentDetails.Rows[rowIndex].Cells[4].FindControl("RBLGender");
                DropDownList DrpQualification = 
                  (DropDownList)grvStudentDetails.Rows[rowIndex].Cells[5].FindControl("drpQualification");
                drCurrentRow = dtCurrentTable.NewRow();
                drCurrentRow["RowNumber"] = i + 1;
                dtCurrentTable.Rows[i - 1]["Col1"] = TextBoxName.Text;
                dtCurrentTable.Rows[i - 1]["Col2"] = TextBoxAge.Text;
                dtCurrentTable.Rows[i - 1]["Col3"] = TextBoxAddress.Text;
                dtCurrentTable.Rows[i - 1]["Col4"] = RBLGender.SelectedValue;
                dtCurrentTable.Rows[i - 1]["Col5"] = DrpQualification.SelectedValue;
                rowIndex++;
            }
            
            ViewState["CurrentTable"] = dtCurrentTable;
            //grvStudentDetails.DataSource = dtCurrentTable;
            //grvStudentDetails.DataBind();
        }
    }
    else
    {
        Response.Write("ViewState is null");
    }
    //SetPreviousData();
}

Now when we run the application, we can see that we can safely add and remove rows dynamically to this GridView.

Note: The sample application is in full working condition. Running the application and debugging it (stepping through it is highly advisable to understand the logic fully and get the gist of what is happening inside).

Point of Interest

This small exercise started as a curiosity to play with ViewState and GridView but ended up as a useful component/logic that can be used in some real scenarios. I hope you will find this useful (although most experienced programmers already might know this stuff, it can still be used by new programmers).

History

• 29 September 2012: First version.
• 03 October 2012: Following has been implemented:
  • Validation for required fields added. 
  • Enter key will now "Add New Row" with newly added row all set to accept data.
  • Saving data into database fucntionality has been implemented.
• 16 October 2012: Following has been implemented:
  • Problem coming after deleting row in Serial No. solved.