Introduction

Today, I will explain Step by Step to Repair Dropdown Boxes in ASP.NET Datagrids. Alright, this issue isn't silverlight, yet I did experience it in my day work. Truth be told, I've experienced it a few times, so I thought I would compose it up so I can discover it once more.

Error

You compose a page that contains an updatable datagrid, which, when in Editmode, contains a dropdown rundown containing lookup things. The Dropdownbox does not populate, and (later when you get it working) the correct listitem is not chosen.

Cause

Since the Dropdownbox down not existing when the page loads, there is nothing to tie.

Step by Step

You need to append your occasions to some non-standard page occasions to get it to work. The pertinent piece of the .aspx page is underneath (placed this in your datagrid)

<asp:TemplateColumn HeaderText=”Tactic Category”>

<HeaderStyle Font-Size=”Large” Font-Bold=”true” />
<ItemTemplate>
<%#DataBinder.Eval(Container.DataItem,”TacticCatName”)%>
</ItemTemplate>
<EditItemTemplate>
<%–Notice the GetCat() routine here as the datasource.–%>
<asp:DropDownList id=”ddTacticCatList” runat=”server” DataSource=”<%# GetCat() %>” DataTextField=”TacticCatName” DataValueField=”TacticCatID”>
</asp:DropDownList>
</EditItemTemplate>
</asp:TemplateColumn>

Your code-behind page should look like this (in C#)

private void MainCode()
{
string strID = Request.QueryString["id"].ToString();
//custom code to get the relevant dataset for the entire datgrid
DataSet ds = LMR.TacticSubCatList(strID);
//custom code to bind to the datagrid
Utility.DGDSNullCheck(ds, dgTacticSubCatList, lblTacticSubCatList, “There are no tactic subcategories in the database at this time.”);
}
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
MainCode();
}
}

protected void dgTacticSubCatList_EditCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
//grab the index
dgTacticSubCatList.EditItemIndex = e.Item.ItemIndex;
MainCode();
}

protected void dgTacticSubCatList_UpdateCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
//get the id value of the selected datagrid item
int intTacticSubCatID = (int)dgTacticSubCatList.DataKeys[(int)e.Item.ItemIndex];

//this gets our textbox, also in the datagrid
TextBox EditText = null;
EditText=(TextBox)e.Item.FindControl(“tbTacticSubCatName”);
string strEditText = Convert.ToString(EditText.Text);

//get the value of our dropdown list
DropDownList dd = (DropDownList)e.Item.FindControl(“ddTacticCatList”);
string strTacticCatID = dd.SelectedValue.ToString();
//do our database update
LMR.TacticSubCatEdit(intTacticSubCatID.ToString(),strTacticCatID,strEditText);
//reset the datagrid
dgTacticSubCatList.EditItemIndex = -1;
//give feedback and rebind
lblFeedback.Text = “Your changes have been applied.”;
MainCode();
}

protected void dgTacticSubCatList_CancelCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
dgTacticSubCatList.EditItemIndex = -1;
MainCode();
}
protected DataTable GetCat()
{
//here is where we get the dataset to populate the dropdown list – it does have to go in an independant function
DataSet ds = LMR.TacticCatList();
return ds.Tables[0];
}

protected void dgTacticSubCatList_ItemDataBound(object sender, DataGridItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.EditItem)
{
//we set the selcted index in the ItemDataBound event
string strID = Request.QueryString["id"].ToString();
string strSubCatID = dgTacticSubCatList.DataKeys[(int)e.Item.ItemIndex].ToString();
Holder.TacticSubCat tsc = LMR.GetTacticSubCat(strSubCatID);
DropDownList dd = (DropDownList)e.Item.FindControl(“ddTacticCatList”);
dd.SelectedIndex =dd.Items.IndexOf(dd.Items.FindByValue(strID));
}
}

It's as simple as that. Hopefully this article will be usefull for you.