I imagine this is quite a common problem, but as yet I haven't found an elegant solution.
I have a number of instances where I have either a ListView or a DetailsView control that is bound to a SQL Server SProc. The problem I have is that there are numerous instances where, when a column is Null, I want to display something different in the UI. A typical example would be where I have a URL column that is rendered as a LinkButton (in the ListViews) or as a HyperLinkField (in the DetailsViews) - when a Null URL is returned, I'm rendering links with no src attribute. Ideally, I's want to display nothing in this field in such a scenario.
In each of these cases, when a null value is returned, how can I skip/alter the rendering of that item?
Thanks in advance.
Update: I haven't had chance to actually try these out, but all helpful suggestions. I think I like Ricks answer the best, but thanks again to the others...
Markup:
<asp:HyperLink id="whatever" runat="server"
NavigateURL='<%# Eval("url") %>' Visible='<%# IsVisible(Eval("url")) %>' />
Code behind:
protected bool IsVisible(object obj)
{
bool result = false;
string url = (string)obj;
if(!string.IsNullOrEmpty(url))
{
result = true;
}
return result;
}
Within a Template bind also to Visibility
<asp:HyperLink ... NavigateURL=<%# Eval("url") %> Visible=<%# Eval("url") != null %> />
Warning: not Tested, could also be
<asp:HyperLink ... NavigateURL=<%# Eval("url") %> Visible=<%# Eval("url") != DBNull.Value %> />
I suppose you could either create a method in your code behind that takes the value as a parameter and returns a link if it's not null. Or you could tap into the data bound event of the Listview, examine the value and hide the control if it's null.
Neither a very elegant solutions, but I guess that's up to you to decide. :)
Related
I want to use a value that is pulled from the SQL within the if statement. Ideally i want to do the equivalent of
<% If DataBinder.Eval(Container, "DataItem.BookID") == 1 Then%>
Is there a way to do this with the correct syntax?
This is how you put conditions in aspx file. Just a rough sample base on what I understand:
<%# System.Convert.ToInt32((DataBinder.Eval(Container.DataItem, "BookID")!="") ? DataBinder.Eval(Container.DataItem, "BookID"):0) %>
Make sure you have int in BookID not any other type.
Explaining Further:
In case you want to have an if else condition:
<%# If DataBinder.Eval(Container.DataItem, "DATAFIELD") <> "" Then
Response.Write("something")
End If %> // This is invalid
The above statement can be properly written in aspx file as this:
<%# DataBinder.Eval(Container.DataItem, "DataField").Equals("")?"":"Something"%>
I'm not sure if this can be done or not the way you are requesting it.
As you may or may not know, the typical way to do this is to have a control in your markup, like so
<asp:listView ID="SophiesListView" ...
..
<ItemTemplate>
<asp:HyperLink ID="hlGlossary" title="click here for more information" target="_blank" runat="server" />
</ItemTemplate>
</asp:listView />
Then, in the codebehind, find your listview / repeater / datagrid or what have you and choose ItemDataBound. Inside this event, do something like this:
If e.Item.DataItem("vehicleType") IsNot DBNull.Value AndAlso e.Item.DataItem("vehicleType") = "JETSKI" Then
DirectCast(e.Item.FindControl("hlGlossary"), HyperLink).NavigateUrl = "Glossary.aspx#JETSKI"
DirectCast(e.Item.FindControl("hlGlossary"), HyperLink).Text = "?"
End If
To keep your page logic as simple as possible your best bet is to data bind to the Visible property of controls. For example, if you want to only show some html if the BookID == 1 then create a new property on your data source like this
public bool Show
{
get
{
return BookID == 1;
}
}
and in your page you'd have
<asp:Placeholder runat="server" Visible='<%# Eval("Show") %>'>
...html goes here...
</asp:Placeholder>
A basic question but there is no such question on Stack Overflow (for ASP.NET)
<asp:TextBox ID="txtUserName" runat="server" Text=<% Session["UserName"] %> >
I did this a week ago, now something is wrong. It should be simple. I also tried <%= %>, it did not work either. Putting a single quote around '<% %>' gives binding error. Help
I normally hide the implementation details from the aspx code with a property:
.cs file
public string UserName { get { return Session["UserName"]; } }
.aspx
<asp:TextBox ID="txtUserName" runat="server" Text='<%= UserName %>' >
What I did was pulled the text box in C# code and set it text value to the session.
Example:
txtUserName.text = Session["UserName"];
Use it in one of the function which checks the session values or you can use in page_load function (the default function for every page)
Now I think your code should look like <asp:TextBox ID="txtUserName" runat="server" Text='<%# Session["UserName"] %>' >
I always forget the sintax for inline code, this information could be helpfull I think.
I have a repeater control and under the ItemTemplate, I have Image control. Anyway the old
How can I set the ImageUrl programatically?
Anyway, the old html code I have was like this:
<ItemTemplate>
<img src="<%# Eval("ImageSource") %>" alt="" />
</ItemTemplate>
But I want to check if the image exists in directory or not then I can setup with temp image.
I have a code but .. it's not really working so there's no sense of showing it here. Can you guys help me? Should I use ItemCreated or ItemDataBound event?
In the xml side in the template, you need to call a method directly.
<asp:Image runat="server" ID="myImg" ImageUrl='<%# MyImageUrlFunction(Eval("DataFieldName").ToString()); %>' />
You need a corresponding method in the code behind defined publicly:
public string MyImageUrlFunction(string field)
{
// put some logic here to determine url
return imageUrl;
}
In your ItemDataBound, do something like:
protected void rpt_ItemDataBound(object sender, RepeaterEventArgs e)
{
HtmlImage img = (HtmlImage)e.Item.FindControl("img");
string imageUrl = (string)DataBinder.Eval(e.Item.DataItem, "ImageSource");
if (File.Exists(imageUrl))
img.Src = imageUrl;
}
That's System.Web.UI.HtmlControls.HtmlImage, System.Web.UI.DataBinder and System.IO.File.
ItemDataBound. You can get the control reference through the current item's findcontrol event, and then check to see that the image exists. You can get the file path using Server.MapPath("~/images/test.png"), and then if it doesn't, inject your own.
You can also use a public method that the client-side markup can call, pass in the URL, and provide a default if it doesn't exist.
HTH.
<ItemTemplate>
<asp:Image ImageUrl='<%# System.IO.File.Exists(Eval("ImageSourceProperty").ToString()) ? Eval("ImageSourceProperty").ToString() : TemporaryImagePath %>' runat="server" />
</ItemTemplate>
for the Error
The server tag is not well formed
You should remove extra space in your code!
<%# System.IO.File......%>
should be <%#System.IO.File......%>
I have a following ListView item template, in which I am trying to bind integer value to Checked property of CheckBox.
IsUploaded value contains only 0 and 1...
<asp:ListView ID="trustListView" runat="server">
<ItemTemplate>
<asp:CheckBox ID="isUploadedCheckBox" runat="server"
Checked='<%# Bind("IsUploaded") %>' />
</ItemTemplate>
</asp:ListView>
But ASP.NET complains that
Exception Details: System.InvalidCastException: Sepcified cast is not valid
Even though following code using DataBinder.Eval() works,
I need to have a 2-way binding, thus need to use Bind().
<asp:CheckBox ID="isUploadedCheckBox2" runat="server"
Checked='<%# Convert.ToBoolean(
DataBinder.Eval(Container.DataItem, "IsUploaded"))) %>' />
How can I convert 0's and 1's to boolean using Bind()?
[ANSWER]
I have extended auto-generated type through partial class by adding a new property mentioned in the answer by Justin
If you're willing to change the class, add a property on the class that's a boolean
public bool IsUploadedBoolean
{
get { return IsUploaded != 0; }
set { IsUploaded = value ? 1 : 0; }
}
If not, you may have success with a TypeConverter:
Create a custom TypeConverter which will handle 0 and 1 to boolean conversions
Stick the TypeConverterAttribute on the IsUploaded property to direct .NET to your custom typeconverter.
How about adding a property to your class which does the conversion?
public bool IsUploadedBool
{
get { return IsUploaded == 1; }
}
and then bind to this IsUploadedBool property instead of directly to the underlying INT.
Marc
Kind of a cheesy work around would be to use a drop down list with list items to give the same effect:
<asp:DropDownList ID="ddlBool" runat="server" SelectedValue= '<%# Bind("IsUploaded") %>'>
<asp:ListItem Text="True" Value="1" />
<asp:ListItem Text="False" Value="0" />
</asp:DropDownList>
For more information visit:
http://dhondiyals.wordpress.com/2010/05/03/binding-checkbox-with-integer-value-in-gridviewtrick/
How about (btw i am using a stored procedure)
Aspx page
<asp:CheckBox ID="social_facebook" runat="server" Checked='<%# Bind("True") %>' />Facebook
Code behind
cmd.Parameters.Add("#p_facebook", SqlDbType.Bit).Value = social_facebook.Checked;
Solution:
Hi, I'm also using Ajax rating inside a GridView and I ran into this problem. After looking through several forums, I tried this and it worked for me. I hope it helps you:
<%# Convert.ToInt32(Eval("EVALUATION")) %>
returns an integer, since you're using Checked which is an integer.
<asp:TextBox ID="tbName" CssClass="formField" MaxLength="<%=Constants.MaxCharacterLengthOfGameName %>" runat="server"></asp:TextBox>
The code above does not work. I can set the MaxLength property of the textbox in the code behind but i rather not. Is there away I can set the MaxLength property in the front-end code as above?
You could use DataBinding:
<asp:TextBox
ID="tbName"
CssClass="formField"
MaxLength="<%# Constants.MaxCharacterLengthOfGameName %>"
runat="server">
</asp:TextBox>
and in your code behind Page_Load call:
tbName.DataBind();
or directly databind the page:
this.DataBind();
The <%= expression %> syntax is translated into Response.Write(expression), injecting the value of expression into the page's rendered output. Because <%= expression %> is translated into (essentially) a Response.Write these statements cannot be used to set the values of Web control properties. In other words, you cannot have markup like the following:
<asp:Label runat="server" id="CurrentTime" Text="<%= DateTime.Now.ToString() %>" />
Source: https://web.archive.org/web/20210513211719/http://aspnet.4guysfromrolla.com/articles/022509-1.aspx
Try to use custom expression builder:
// from http://weblogs.asp.net/infinitiesloop/archive/2006/08/09/The-CodeExpressionBuilder.aspx
[ExpressionPrefix("Code")]
public class CodeExpressionBuilder : System.Web.Compilation.ExpressionBuilder
{
public override CodeExpression GetCodeExpression(BoundPropertyEntry entry,
object parsedData, ExpressionBuilderContext context)
{
return new CodeSnippetExpression(entry.Expression);
}
}
And then use it like
<asp:TextBox ID="tbName" CssClass="formField" MaxLength="<%$ Code: Constants.MaxCharacterLengthOfGameName %>" runat="server"></asp:TextBox>
As Ropstah said, it isn't going to work with the <%= expression %> syntax.
But you could probably use databinding, which just requires that you use the <%# expression %> syntax and then call MyTextBox.Databind in CodeBehind.
Of course, at that point it might be more clear to just do the whole operation in CodeBehind.
Another alternative: if you really want this to be declarative, you could get away from the Label and embed your expression in a span tag.That way you still get to apply CSS, etc and I think the <%= expression %> syntax would work.
Why don't you just set it in the Page_Init callback function in the code behind?
This example is geared towards getting the max length from underlying sql types in linq. But you should be able to customise it to your needs
http://blog.binaryocean.com/2008/02/24/TextBoxMaxLengthFromLINQMetaData.aspx
It looks like you want to be able to control the max length of a specific type of text box from a single location so that if that max length needs to change, you only need to change it in one place.
You can accomplish this by using a skin file. You set the max length in the skin file as you would normally and then any textbox that uses that max length would use the skin. If the length changes then you only need to change the skin file.
You can do it with databinding
<asp:TextBox
ID="tbName"
CssClass="formField"
MaxLength='<%# Constants.MaxCharacterLengthOfGameName %>'
runat="server" />
Then in the code behind
protected void Page_Load(object sender, EventArgs e) {
Page.DataBind();
}
You can embed "normal" code in the .aspx file if you so want, like:
<%
tbName.MaxLength = Constants.MaxCharacterLengthOfGameName
%>
<asp:TextBox ID="tbName" CssClass="formField" runat="server"></asp:TextBox>
This harkens back to an older style "classic" ASP way of doing this.