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5.4

ASP.NET: Retrieving DropDownList in Gridview RowUpdating event

Asked by BigBadJock in Programming for ASP.NET, C# Programming Language, .NET Framework 3.x versions

Tags: ASP.NET; .Net, C#; GridView; DropDownList

I have a problem, with GridView and TemplateFields. We have an application which creates maintenance screens based on an xml configuration file. The xml describes which fields to show, etc. This all works

However, we have a new requirement to add DropDownLists to some columns to enforce data integrity.

I have therefore added the relevant xml, and when creating the grid, create the column as a TemplateField and the EditItem as a DropDownList with its own SqlDataSource.

So far so good, this all works, the grid is displayed, the DropDownList appears, filled with the correct data, shows the correct initial item and lets the user select another.

Here is where I have problems. The when trying to get the value from the DropDownList in the RowUpdating event, I cant find it. Ive used FindControl to no avail. I create a RecursiveFindControl method that ran through every control on the page, and it cant find it. Ive tried peeking in the cell controls in the debugger and its just not there.

Can anyone help? Ive duplicated it in a simpler test page, with a test database.

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             <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="test2.aspx.cs" Inherits="WareHouseAdmin.test2" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" AutoGenerateEditButton="True" onrowcancelingedit="GridView1_RowCancelingEdit" onrowediting="GridView1_RowEditing" onrowupdated="GridView1_RowUpdated" onrowupdating="GridView1_RowUpdating" DataSourceID="SqlDataSource1">
        </asp:GridView>
    </div>
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" onupdated="SqlDataSource1_Updated" onupdating="SqlDataSource1_Updating"></asp:SqlDataSource>
    <asp:SqlDataSource ID="SqlDataSource2" runat="server"></asp:SqlDataSource>
    </form>
</body>
</html>
 
 
-----------------------------
 
 
 
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
 
namespace WareHouseAdmin
{
    public partial class test2 : System.Web.UI.Page
    {
        
        protected void Page_Init(object sender, EventArgs e)
        {
            SetupData();
        }
 
        protected void Page_Load(object sender, EventArgs e)
        {
            BuildGrid();
            if (!IsPostBack)
            {
                BindGrid();
            }
        }
 
        private void SetupData()
        {
            string connection = ConfigurationManager.ConnectionStrings["warehouseConnectionString"].ConnectionString;
            this.SqlDataSource1.ConnectionString = connection;
            this.SqlDataSource1.SelectCommand = "select * from songs";
            this.SqlDataSource1.UpdateCommand = "UPDATE [Songs] SET [AlbumId]=@albumId, [ArtistId]=@artistId, [SongTitle] = @SongTitle, [notes] = @notes WHERE [ID] = @ID";
            this.SqlDataSource1.UpdateParameters.Clear();
 
            this.SqlDataSource2.ConnectionString = connection;
            this.SqlDataSource2.SelectCommand = "select * from albums";
        }
 
        private void BindGrid()
        {
            this.GridView1.DataBind();
        }
 
        private void BuildGrid()
        {
            this.GridView1.Columns.Clear();
            AddColumn("id", "id", "Int32");
            //AddColumn("Album", "albumId", "Int32");
            AddDropDownColumn("Album", "albumId","id","name",SqlDataSource2);
            AddColumn("Artist", "artistId", "Int32");
            AddColumn("Title", "songTitle","String");
            AddColumn("Notes", "notes", "String");
 
            this.GridView1.DataKeyNames = new string[] { "id" };
 
        }
 
 
        private void AddColumn(string header, string name, string dataType)
        {
            BoundField bf = new BoundField();
            bf.HeaderText = header;
            bf.DataField = name;
            bf.SortExpression = name;
            bf.ReadOnly = false;
            bf.HtmlEncode = true;
            this.GridView1.Columns.Add(bf);
 
 
            TypeCode tc = (TypeCode)Enum.Parse(typeof(TypeCode), dataType);
            Parameter p = new Parameter(name, tc);
            this.SqlDataSource1.UpdateParameters.Add(p);
 
        }
 
        private void AddDropDownColumn(string header, string name, string valueColumn, string displayColumn, SqlDataSource dataSource)
        {
            TemplateField tf = new TemplateField();
            tf.HeaderText = header;
            tf.ItemTemplate = new DDLTemplate(ListItemType.Item, name, null, null, null);
            tf.EditItemTemplate = new DDLTemplate(ListItemType.EditItem, name, valueColumn, displayColumn, dataSource );
            this.GridView1.Columns.Add(tf);
 
            TypeCode tc = (TypeCode)Enum.Parse(typeof(TypeCode), "Int32");
            Parameter p = new Parameter(name, tc);
            this.SqlDataSource1.UpdateParameters.Add(p);
 
        }
 
        protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
        {
            this.GridView1.EditIndex = e.NewEditIndex;
            BindGrid();
        }
 
        protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            GridViewRow row = this.GridView1.Rows[e.RowIndex];
            Control foundControl = RecursiveFindControl(row, "GridView1$ctl07$albumId_ddl");
            if (foundControl != null)
            {
                DropDownList ddl = (DropDownList)foundControl;
                string val = ddl.SelectedValue;
                e.NewValues.Add("albumId", val);
            }
            BindGrid();
        }
 
        private Control RecursiveFindControl(Control root, string id)
        {
            if (root.ID != null)
            {
                if (root.ID.EndsWith(id))
                {
                    return root;
                }
            }
            if (root.ClientID != null)
            {
                if (root.ClientID.EndsWith(id))
                {
                    return root;
                }
            }
            foreach (Control subControl in root.Controls)
            {
                Control foundControl = RecursiveFindControl(subControl, id);
                if (foundControl != null)
                {
                    return foundControl;
                }
            }
            return null;
        }
 
        protected void GridView1_RowUpdated(object sender, GridViewUpdatedEventArgs e)
        {
        }
 
        protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
        {
            this.GridView1.EditIndex = -1;
            BindGrid();
        }
 
        protected void SqlDataSource1_Updated(object sender, SqlDataSourceStatusEventArgs e)
        {
            if (e.Exception != null)
            {
                e.ExceptionHandled = true;
            }
        }
 
        protected void SqlDataSource1_Updating(object sender, SqlDataSourceCommandEventArgs e)
        {
            System.Console.WriteLine(e.Command);
 
        }
 
    }
 
    public class DDLTemplate : System.Web.UI.Page, ITemplate
    {
        ListItemType templateType;
        string column;
        string valueColumn;
        string displayColumn;
        SqlDataSource dataSource;
 
        public DDLTemplate(ListItemType type, string column, string valueColumn, string displayColumn, SqlDataSource dataSource)
        {
            this.templateType = type;
            this.column = column;
            this.valueColumn = valueColumn;
            this.displayColumn = displayColumn;
            this.dataSource = dataSource;
        }
 
        public void InstantiateIn(System.Web.UI.Control container)
        {
            switch (templateType)
            {
                case ListItemType.Header:
                    break;
 
                case ListItemType.Item:
                    Literal lc = new Literal();
                    lc.DataBinding += new EventHandler(lc_DataBinding);
                    container.Controls.Add(lc);
                    break;
 
                case ListItemType.EditItem:
                    DropDownList ddl = new DropDownList();
                    ddl.ID = "albumId_ddl";
                    ddl.DataValueField = this.valueColumn;
                    ddl.DataTextField = this.displayColumn;
                    ddl.DataSource = this.dataSource;
                    ddl.DataBinding += new EventHandler(ddl_DataBinding);
                    ddl.SelectedIndexChanged += new EventHandler(ddl_SelectedIndexChanged);
                    container.Controls.Add(ddl);
                    break;
 
                case ListItemType.Footer:
                    break;
 
            }
        }
 
        void ddl_SelectedIndexChanged(object sender, EventArgs e)
        {
            DropDownList ddl = (DropDownList)sender;
            Session["albumId_val"] = ddl.SelectedValue;
        }
 
        void lc_DataBinding(object sender, EventArgs e)
        {
            Literal lc = (Literal)sender;
            GridViewRow row = (GridViewRow)lc.NamingContainer;
            string text = DataBinder.Eval(row.DataItem, this.column).ToString();
            lc.Text = text;
        }
 
        void ddl_DataBinding(object sender, EventArgs e)
        {
            DropDownList ddl = (DropDownList)sender;
            GridViewRow row = (GridViewRow)ddl.NamingContainer;
            string id = DataBinder.Eval(row.DataItem, column).ToString();
            ddl.SelectedValue = id;
            ddl.SelectedIndexChanged += new EventHandler(ddl_SelectedIndexChanged);
 
        }
 
    }
 
}

           
         

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ASP.NET: Retrieving DropDownList in Gridview RowUpdating event

Asked by BigBadJock in Programming for ASP.NET, C# Programming Language, .NET Framework 3.x versions

Tags: ASP.NET; .Net, C#; GridView; DropDownList

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