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ASP.NET Questionnaire I

What is the difference between Bind() and Eval()?

Eval is a one way(read only) binding. This method is used when you want to bind value to a readonly control like Label.

Bind is a two way(read/write) binding. This method is used when you want to bind value to a read/write control like textbox.

If Eval is used for two way binding, then an error occurs. Consider an example

<asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSource1" AutoGenerateColumns="False"
        DataKeyNames="testid">
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <%# Eval("testname")%>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="edtName" runat="server" Text='<%# Eval("testname") %>' />
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:CommandField ShowEditButton="True"></asp:CommandField>
        </Columns>
    </asp:GridView>
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:TestingConnectionString %>"
        SelectCommand="SELECT [testid], [testname] FROM [test12]" UpdateCommand="Update [test12] SET [testname]=@testname WHERE [testid]=@testid"></asp:SqlDataSource>

Here in edititemtemplate Eval() is used instead of Bind(). So you run this program and try to update the record you will get this error -

Must declare the scalar variable "@testname".

If Eval() is changed to Bind() then this program will work fine.

How to set the DefaultButton of a content page in asp.net?

Page.Form.DefaultButton = <button_name>.UniqueID

How can we identify that the Page is Post Back?

We can identify if the page is postback or not using IsPostBack property. On page load event if the value of IsPostBack is true then it means the page is postback.

Which is the parent class of the Web server control?

System.Web.Ul.Control

Posted By -

Karan Gupta

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