Replacing an image URL with a C# string

Question

I've been looking about and cant figure out how to get a value from C# into the tag on an ASPX page. I've tried a number of options but not getting anywhere.

When my asp page loads, a value is obtained using queryString from the pages url (ie mypage.aspx?app=safety ) It then runs a switch to find out what image url to use on the page.

Thing is, I get a Compilation Error "The name 'img_small' does not exist in the current context". What do you think of my code below? I cant see what Im missing!

C#:

protected void Page_Load(object sender, EventArgs e)
{
    string img_small;

    String appName = Request.QueryString["app"];

    switch (appName)
    {
        case "safety":
            img_small = "safety-logo.png";
            break;

        case "files":
            img_small = "files-logo.png";
            break;

        case "drawings":
            img_small = "drawings-logo.png";
            break;

        case "specs":
            img_small = "specs-logo.png";
            break;

        default:
            img_small = "idms-logo.png";
            break;
    }
}

HTML:

<img src='"<%=img_small%>"' />

Answer 1

img_small doesn't exist outside of Page_Load .

You need to use at a minimum an internal field with that name in order to be able to access it anywhere in the class, including the .aspx .

public string img_small;

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

Answer 2

This is because img_small is a local variable of Page_Load function, it doesn't exist outside this function. This is why you get this error.

I'd suggested you to change

<img src='"<%=img_small%>"' />

to

<asp:Image ID='imgImage' runat='server' />

And then at the bottom of Page_Load function do

imgImage.ImageUrl = img_small;