Setting imageURL using a function in ASP.NET

Question

I've done this task before within repeaters and it has worked. However I can't get the below to work for me in a normal webforms page. The images appear as broken links and breakpoints I put in the codebehind are not triggered.

(in the aspx file)

<asp:ImageButton ID="ImageButton1" runat="server" ImageUrl='<%# GetImageDirectory()%>btnRunReport.png'  />

(codebehind)

public string GetImageDirectory()
{
    return "~/App_Variants/LBSX/images/";
}

This is the second method I've tried, in the other one I tried passing the imagename through as a string, and it would return the entire link that way. Still no luck!

Any thoughts?

Thanks!

[EDIT] Thanks for the help everyone. In the end after the handy hints I found a recursive snippet which did the trick as follows:

private void UpdateImages(Control Parent)
{
    foreach (Control c in Parent.Controls)
    {
        ImageButton i = c as ImageButton;
        if (i != null)
        {
            i.ImageUrl = "~/App_Variants/LBSX/images/" + i.ImageUrl;
        }
        if (c.HasControls())
        {
            UpdateImages(c);
        }
    }
}

protected void Page_Load(object sender, EventArgs e)
{
    UpdateImages(Page);
    ...

Hope it helps someone else.

Cheers

<%# - call on data-bind event. <%= - call in render (normal usage). you're looking for <%= — RPM1984
– RPM1984, Commented Jul 19, 2010 at 5:54
Yes, sorry I also have tried the <%= but still no breakpoint triggered. What else could I be doing wrong? — Glinkot
– Glinkot, Commented Jul 19, 2010 at 6:23
Also, when I view source on the page, the control shows the src as: src="<%=GetImageDirectory()%20%>" rather than trying to pass whatever it calculates. Maybe there's a clue there — Glinkot
– Glinkot, Commented Jul 19, 2010 at 6:42

Giuseppe Accaputo · Accepted Answer · 2010-07-19 10:41:32Z

6

First, just like Zachary mentioned, you're using the code block for data binding.

Second, as you've already tried, using an inline expression (<%= %>) won't work either in your case, since you can't use an inline expression for any property of a server-tag.

What you could do instead is defining an image button using HTML syntax, omitting the runat="server" tag, and use the inline expression to get your image's URL:

<input type="image" src="<%= GetImageDirectory() %>btnRunReport.png" name="image" />

What an inline expression does is, it calls Response.Write() with the value between <%= %> as the parameter, e.g. <%= this.MyVar %> is Response.Write(this.MyVar).

edited Jul 19, 2010 at 10:41

answered Jul 19, 2010 at 7:04

Giuseppe Accaputo

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4 Comments

Glinkot Over a year ago

Ok, thanks for that. What I'm trying to do is put a custom directory (depending on certain conditions) in front of the image name. So in one case it may be images3/picture.jpg and in others it would be images4/picture.jpg. I'm not using themes for various reasons. Is there any way in the codebehind I could achieve the same by doing something like: First, set imageURL at designtime to 'picture.jpg' without path Then for each Imagebutton in (whatever the page object is) ImageUrl = "mydirectory" + existing imageurl Would that be workable do you think? Thanks for your time!

Glinkot Over a year ago

Thanks to your guidance I've now managed to solve this. Ended up iterating through the controls as mentioned and putting the path at the front. Works a charm! I will add code to the question for others reference.

Giuseppe Accaputo Over a year ago

I'm glad you could solve this. I've managed to write the code for iterating through the controls; if somebody's interested, you can find the mentioned code here: hpaste.org/fastcgi/hpaste.fcgi/view?id=27788#a27788

Glinkot Over a year ago

Thanks for that, much appreciated mate. Note that the one I put above is recursive whereas yours seems to be nested to two levels. Not sure if it ever goes below two levels, mind you... :)

Zachary · Accepted Answer · 2010-07-19 05:37:52Z

2

Your syntax is for data binding, <%# %>. If you are just trying to do inline c#, you should use <%= %>.

answered Jul 19, 2010 at 5:37

Zachary

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1 Comment

Glinkot Over a year ago

Actually I should have mentioned, I've tried that also and no luck still! Good point though, I did find various people saying that when I was searching forums etc.

Trung Nguyen · Accepted Answer · 2014-01-08 10:21:19Z

I give you another solution. Use ExpressionBuilder :

Create a class devired from ExpressionBuilder and override function GetCodeExpression

 namespace your.namespace
{
public class CustomBuilder : ExpressionBuilder
{
    public override CodeExpression GetCodeExpression(BoundPropertyEntry entry, object parsedData, ExpressionBuilderContext context)
    {
        Type type1 = entry.DeclaringType;
        PropertyDescriptor descriptor1 = TypeDescriptor.GetProperties(type1)[entry.PropertyInfo.Name];
        CodeExpression[] expressionArray1 = new CodeExpression[1];
        expressionArray1[0] = new CodePrimitiveExpression(entry.Expression.Trim());

        String temp = entry.Expression;
        return new CodeCastExpression(descriptor1.PropertyType, new CodeMethodInvokeExpression(new
       CodeTypeReferenceExpression(base.GetType()), "GenerateLink", expressionArray1));
    }
    public static  String GenerateLink(String link)
    {
        return ConfigurationManager.AppSettings["MediaPath"] + link + "?ver=" + ConfigurationManager.AppSettings["MediaCode"];
    }
}
}

expressionArray1 is the input array for GenerateLink function. You can change the size of array according to numbers of input params for your function

2.Register your expression in webconfig

<system.web>
    <compilation debug="true" targetFramework="4.0" >
      <expressionBuilders>

        <add expressionPrefix="GenLink" type="your.namespace.CustomBuilder"/>
      </expressionBuilders>

    </compilation>

3.In view your can use new expression:

<asp:ImageButton ID="ImageButton1" runat="Server" ImageUrl='<%$ GenLink:images/magnifier.jpg %>'/>

4.Enjoy !!!

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