Why isn't this working?
<ajaxToolkit:TabPanel Enabled='<%# User.IsInRole("admin") %>'...
While this works:
<asp:TextBox Enabled='<%# User.IsInRole("admin") %>'...
Is the first example within a binding context (bound control)? Perhaps you want to use the output directive instead of the binding directive?
<ajaxToolkit:TabPanel Enabled='<%= User.IsInRole("admin") %>'
EDIT: My bad. <%= %> translates into Response.Write, which is not what you want -- too used to ASP.NET MVC, I guess. The best thing is to make it runat="server", give it an ID and set the value in your code-behind.
<ajaxToolkit:TabPanel runat="server" ID="myTabs" ... />
protected void Page_Load( object sender, EventArgs e )
{
myTabs.Enabled = User.IsInRole("admin");
...
}
Related
I'm not sure if I am asking this question correctly. I know that I can accomplish what I need in code behind, but I'm wondering if this is possible. I want to hide a control if there is a value in another control. I know I can use databinder.eval in a repeater, but can I use it just for a normal asp control on the page?
In other words, I want to do something like this:
<asp:TextBox runat="server" ID="ConditionalText" Text="Show if other value is empty" Visible ='<%# testValue.Text != "" ? false : true %>'></asp:TextBox>
<asp:TextBox runat="server" ID="testValue"></asp:TextBox>
I tried just the way I have it above, and <%# testValue. exposed available properties of "testValue" TextBox so I thought it might work. It didn't throw any errors but it did not show/hide the textbox. I'm just wondering if this is possible and what I would have to do to accomplish this.
Any assistance is greatly appreciated.
It can work, but since you are using a databinding expression outside a GridView, Repeater etc. you have to call it manually.
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack == false)
{
//rest of the code
}
//call databind manually
DataBind();
}
PS better to use IsNullOrEmpty instead of = ""
<asp:TextBox runat="server" ID="ConditionalText" Text="Show if other value is empty"
Visible='<%# !string.IsNullOrEmpty(testValue.Text) ? false : true %>'></asp:TextBox>
In my ASP .NET Web Forms I have the following declarative code:
<asp:TextBox runat="server" ID="txtbox" CssClass='<%=TEXTBOX_CSS_CLASS%>' />
The constant TEXTBOX_CSS_CLASS is defined in a base class that the page's code-behind class inherits from:
public class MyPageBase : Page
{
protected internal const string TEXTBOX_CSS_CLASS = "myClass";
}
The edit-time compiler however warns me that "This is not scriptlet [sic]. Will output as plain text".
True to its word, the css class is rendered as literally "<%=TEXTBOX_CSS_CLASS%>".
What does this error message mean and is there a workaround so I can still use a constant in a base class?
You cannot use <%= ... %> to set properties of server-side controls.
Inline expressions <% %> can only be used at
aspx page or user control's top document level, but can not be embeded in
server control's tag attribute (such as <asp:Button... Text =<% %> ..>).
If your TextBox is inside a DataBound controls such as GridView, ListView .. you can use: <%# %> syntax. OR you can call explicitly DataBind() on the control from code-behind or inline server script.
<asp:TextBox runat="server" ID="txtbox" class='<%# TEXTBOX_CSS_CLASS %>' />
// code Behind file
protected void Page_Load(object sender, EventArgs e)
{
txtbox.DataBind();
}
ASP.NET includes few built-in expression builders that allows you to extract custom application settings and connection string information from the web.config file. Example:
Resources
ConnectionStrings
AppSettings
So, if you want to retrieve an application setting named className from the <appSettings> portion of the web.config file, you can use the following expression:
<asp:TextBox runat="server" Text="<%$ AppSettings:className %>" />
However, above snippet isn't a standard for reading classnames from Appsettings.
You can build and use either your own Custom ExpressionBuilders or Use code behind as:
txtbox.CssClass = TEXTBOX_CSS_CLASS;
Check this link on building Custom Expression builders.
Once you build your custom Expression you can display value like:
<asp:TextBox Text="<%$ SetValue:SomeParamName %>"
ID="setting"
runat="server" />
The problem is that you can't mix runat=server controls with <%= .. %>code blocks. The correct way would be to use code behind: txtbox.CssClass = TEXTBOX_CSS_CLASS;.
This will work.
Mark up
<asp:TextBox runat="server" ID="txtbox" class='<%# TEXTBOX_CSS_CLASS %>' />
Code-behind
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
txtbox.DataBind();
}
}
But its a lot cleaner to access the CssClass property of the asp:TextBox on Page_Load
I have an ASP control custom built and I need to pass a value taken from a session variable to it like so:
<custom:control id='mycontrol' value="+Session['myControlValue']+">
...
</custom:control>
the above code obviously doesn't work, I need a way to insert the Session value in the control in this way somehow, can anyone help?
If it is a data bound control you may try this:
<custom:control id="mycontrol"
runat="server"
value='<%# Session["myControlValue"] %>'>
</custom:control>
Personally I would prefer setting this value from the code behind. It seems a little strange to me that a view (aspx) page manipulates the session:
protected void Page_Load(object sender, EventArgs e)
{
mycontrol.Value = Session["myControlValue"];
}
Switch the quotes, like so:
<custom:control id="mycontrol"
runat="server"
value='<%# Session["myControlValue"] %>' />
This works:
<span value="<%= this.Text %>" />
This doesn't work:
<asp:Label Text="<%= this.Text %>" runat="server" />
Why is that?
How can I make the second case work properly, i.e., set the label's text to the value of the "Text" variable?
Use Data binding expressions
<asp:Label ID="Label1" runat="server" Text="<%# DateTime.Now %>" ></asp:Label>
Code behind,
protected void Page_Load(object sender, EventArgs e){
DataBind();
}
you can do this
<asp:Label ID="Label1" runat="server" ><%= variable%></asp:Label>
You will need to set the value of the server control in code
First of all, assign an ID to the label control so you can access the control
<asp:Label ID="myLabel" runat="server" />
Then, in your Page_Load function, set the value of your labels 'Text' field
protected void Page_Load(object sender, EventArgs e)
{
myLabel.Text = 'Whatever you want the label to display';
}
This function will be in your code behind file, or, if you are not using the code behind model, inside your aspx page you will need
<script runat="server">
protected void Page_Load(object sender, EventArgs e)
{
myLabel.Text = 'Whatever you want the label to display';
}
</script>
Good luck.
In my code i am using something like this easily but in the databound control like ListView Item template
<asp:HyperLink ID="EditAction" class="actionLinks" Visible='<%#Eval("IsTrue").ToString() != "True"%>' runat="server" NavigateUrl='<%# Eval("ContentId","/articles/edit.aspx?articleid={0}")%>' />
But when i tried to use outside the databound control using <%# .. %>, it simply doesn't work.
You can easily do with
My href
But for server controls, and outside of databound control. We need to call DataBind() in pageload event explicitly
<asp:Hyperlink ID="aa" NavigateUrl='<%#myHref%>' >
Not sure how to mark this as such, but this is a bit of a duplicate. See this thread.
I don't think embedding code in to your markup will really make your markup any clearer or more elegant.
<asp:Label> is compiling at runtime and converting to html tags. You can set text with codebehind or like this:
<asp:Label id="Text1" runat="server" />
<% Text1.Text = this.Text;%>
UPD: Seems like my variant doesnt work, this is better:
protected void Page_Load(object sender,EventArgs e)
{
Text1.Text = this.Text;
}
Just pitching this little nugget in for those who want a good technical breakdown of the issue -- https://blogs.msdn.microsoft.com/dancre/2007/02/13/the-difference-between-and-in-asp-net/
I think the crux is in pretty decent agreement with the other answers:
The <%= expressions are evaluated at render time
The <%# expressions are evaluated at DataBind() time and are not evaluated at all if DataBind() is not called.
<%# expressions can be used as properties in server-side controls. <%= expressions cannot.
Why cant i use code nuggets to set a control property??For example a validationgroup of a button or the text property of a label.
<asp:Button ID="btn" runat="server" Text="test" ValidationGroup='<% =TestValidate %>'
<asp:Label ID="lbl" runat="server" Text='<% =Test %>' />
Is there any way to set a controls properties without using codebehind?
You could use data binding:
<asp:Label ID="lbl" runat="server" Text='<%# "Hello World" %>' />
provided that you call DataBind in code behind:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
DataBind();
}
}
<%=SomeVar %> uses late binding which behaves like a Response.Write (in Page.PreRender, if I remember correctly). Hence it will not be utilized by the server controls like the way you wanted it. Unless you use code-behind or inline-code-behind to perform binding.