Interview Questions → ASP.NET → ASP.NET Questionnaire I

ASP.NET Questionnaire I

What is the difference between literal and label?

The difference lies in the way both controls renders HTML. Consider both controls

<!--Label control-->    
<asp:Label runat="server" Text="Label Control"></asp:Label>
<!--Literal control-->    
<asp:Literal runat="server" Text="Literal Control"></asp:Literal>

The rendered HTML is

<!--Label control-->    
<span>Label Control</span>
<!--Literal control-->    
Literal Control

So the difference is

      1. When label control is rendered the text is enclosed in span tag, whereas literal control text is rendered without any tag.

      2. In label control we can apply style using the CssClass property, whereas in literal control there is no property to apply style. But you can use HTML tags in the Text property of the control.

      3. Label control is inherited from WebControl class whereas Literal control is inherited from Control class.

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

Query/Feedback

Your Email Id		**

Subject		*

Query/Feedback	Characters remaining 250	**