IT

Many Databinding settings can be expressed declaratively.

• Example - Setting a HyperLink "Text" and "NavigateURL" properties declaratively:

<asp:HyperLink runat="server" ID="categoryHyperLink" 
    Text='<%#String.Format("{0} ({1})", Eval("CategoryName"), Eval("TotalProducts")) %>'
    NavigateUrl='<%# "~/SomeURL.aspx?id=" + Eval("CategoryID") %>' />

This would result in a link like "Vegetables (4)", whose URL would pass the "CategoryID" has the querystring "id" parameter.

• In some more complex situations a call to a method can be used, for example the "Text" propertie from the example above could be replaced with:

Text='<%# getCategoryWithTotalProducts((string)Eval("CategoryName"), 
                                       (int)Eval("NumberOfProducts"))%>'

where getCategoryWithTotalProducts method would be defined in the code behind:

protected string getCategoryWithTotalProducts(string categoryName, int totalProducts)
{        
    return String.Format("{0} ({1})", categoryName, totalProducts);        
}

Many ASP.NET Web Controls have two distinct DataSource properties, and only one can be set at a given time:

• DataSource: can be set directly to a an object like a DataTable;
• DataSourceID: can be set to a DataSource Control ID like an "ObjectDataSource", an "SQLDataSource", etc.;

• Example using the DataSource property on a Repeater Web Control (set on code-behind):

The aspx file:

<asp:Repeater ID="CategoriesRepeater" runat="server" >
    <HeaderTemplate><ul></HeaderTemplate>
    <FooterTemplate></ul></FooterTemplate>
    <ItemTemplate>
        <li>
            <asp:HyperLink runat="server" ID="categoryHyperLink" 
                Text='<%#String.Format("{0} ({1})", Eval("CategoryName"), Eval("NumberOfProducts")) %>'
                NavigateUrl='<%# "~/DataListRepeaterBasics/CategoriesAndProducts2.aspx?id=" + Eval("CategoryID") %>' />
        </li>
    </ItemTemplate>        
</asp:Repeater>

The cs file:

protected void Page_Load(object sender, EventArgs e)
{
    CategoriesRepeater.DataSource = getCategories();
    CategoriesRepeater.DataBind();
}

protected Northwind.CategoriesDataTable getCategories()
{
    CategoriesBLL categoriesAPI = new CategoriesBLL();
    return categoriesAPI.GetCategoriesAndNumberOfProducts();
}

The DataBind() method must be called after setting the DataSource property to actually bind the data to the Web Control.

• Example using the DataSourceID property to an ObjectDataSource (set declaratively):

 <asp:Repeater ID="CategoriesRepeater" runat="server"
    DataSourceID="CategoryDataSource">
    <HeaderTemplate><ul></HeaderTemplate>
    <FooterTemplate></ul></FooterTemplate>
    <ItemTemplate>
        <li>
            <asp:HyperLink runat="server" ID="categoryHyperLink" 
                Text='<%#String.Format("{0} ({1})", Eval("CategoryName"), Eval("NumberOfProducts")) %>'
                NavigateUrl='<%# "~/DataListRepeaterBasics/CategoriesAndProducts2.aspx?id=" + Eval("CategoryID") %>' />
        </li>
    </ItemTemplate>       
</asp:Repeater>
<asp:ObjectDataSource ID="CategoryDataSource" runat="server" 
    OldValuesParameterFormatString="original_{0}" 
    SelectMethod="GetCategoriesAndNumberOfProducts" TypeName="CategoriesBLL">
</asp:ObjectDataSource>