Recently though I’ve been working in an environment where they are big fans of Microsoft controls, so as a wise man once said ‘When in Rome use the same ASP.Net controls as the Romans do’. With that in mind I have been getting my hands dirty with DataGrids, DataViews and Repeaters. One of the things that has always put me off of these controls is which control do you use for what. The confusion was so great that often I had 2 or 3 different controls on a page at one time to compare, contrast and moan about. The result of all this moaning/development was
- For paging – use a DataGrid
- For an easy primary key for each row – use a DataGrid
- For multiple columns – use a DataView
- For fine control over what is displayed on each cell – Moan a lot then go back to using a dynamic collection of TableCells (that designers will never, ever be able to see).
But then as I was walking on the road to Damascus (a local falafel shop) a bright light shone from the clouds and a wise voice spake unto me and said “don’t mess around with all those other controls – just use Repeaters”. Thus and verily I journeyed back to the promised land and recoded all my grids with repeaters using the following divinely inspired techniques to get over the aforementioned limitations.
Primary Key for each Row
Use a hidden field (i.e. label with visibility set to false) and write the value into that
<asp:Repeater runat="server">
<ItemTemplate>
<asp:Literal ID="lblPrimaryKey" runat="server" Visible="false"
Text='<%# DataBinder.Eval(Container.DataItem, "PrimaryKeyId") %>' />
<%# DataBinder.Eval(Container.DataItem, "Name") %>
<%# DataBinder.Eval(Container.DataItem, "Address") %>
<%# DataBinder.Eval(Container.DataItem, "DoB")%>
</ItemTemplate>
</asp:Repeater>protected void Repeater1_ItemCreated(object sender, RepeaterItemEventArgs e)
{
Control lblKey = item.FindControl("lblPrimaryKey");
Int primaryKey = Int32.Parse(lblKey.Text);
//do something with the primary key
};Use divs for the columns and float them to the left (see http://css.maxdesign.com.au/floatutorial/ for float tutorial). The below code shows it in action.
The above example gives 4 columns i.e. 800px box surrounding the repeater with divs of 200px floated inside – sooo only 4 can fit before a new row is started. Obviously you don’t need to be a maths genius to work out the numbers for other numbers of columns (e.g. 600px outside, 200px divs – 3 columns etc…).<asp:Repeater ID="Repeater1" runat="server">
<HeaderTemplate>
<div style="width:800px;">
</HeaderTemplate>
<ItemTemplate>
<div style="width:200px;float:left;"><%# DataBinder.Eval(Container.DataItem, "DisplayField")%></div>
</ItemTemplate>
<FooterTemplate>
</div>
</FooterTemplate>
</asp:Repeater>
Fine control over each cell
If you have a requirement to modify each cell depending on the primary key of the row – leverage the On_ItemDataBound event of the repeater grid and modify the contents of each cell as it’s rendered
<asp:Repeater ID=" Repeater1" runat="server"
OnItemDataBound="Repeater1_ItemCreated">
<ItemTemplate>
<asp:Literal ID="lblPrimaryKey" runat="server" Visible="false"
Text='<%# DataBinder.Eval(Container.DataItem, "PrimaryKeyField")%>' />
<%# DataBinder.Eval(Container.DataItem, "Name") %>
<%# DataBinder.Eval(Container.DataItem, "Address") %>
<asp:Button ID="btnGo" runat="server" Text="Details" />
</ItemTemplate>
</asp:Repeater>It the above example we could control the button activity based on the primary key in the repeater row.protected void rptSurveyListNao_ItemCreated(object sender,
RepeaterItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item
e.Item.ItemType == ListItemType.AlternatingItem)
{
Control lblSurveyStatus = item.FindControl("lblPrimaryKey");
Int primaryKey = Int32.Parse(lblSurveyStatus.Text);
If(primaryKey > 0)
{
btnGo = (Button)item.FindControl("btnGo");
btnGo.Enable = true;
}
}
}
Paging
Use the PagedDataSource following the technique outlined in 4GuysFromRolla. . OK hands up for this one – I’ve never used it but I’ve been assured by real life people that it works
And from that day forward all the HTML coders and designers in the land
came to pay homage to the lowly Repeater because they could easily access the
HTML tags behind the controls and not struggle with the arcane DataGrid styling
properties.
