Introduction
Usually a Silverlight application is not allowed to access a FileInfo
's full path attribute, even via reflection. This is because of the security policy.
But sometimes, for our applications, we need to store a file's path, especially if talking about network directories. To workaround this, we can use JavaScript! Honesty I hate JavaScript, but sometimes there is no other way. Silverlight is even too much secure for production applications! :-)
The basic idea is to grant access to path by using JavaScript and then send back the value to Silverlight for our use.
Note
This solution will perfectly work on Internet Explorer, will only show file name on Firefox and won't work on Chrome, because of Input element implementation... :@
If you have any solution to this, please report it to me and I will update this tip page! :-)
Background
Please refer to this article if you don't know how Silverlight/JavaScript communication works.
Using the Code
1. Edit HTML/ASPX Page
First let's add this script
code to our head element:
<script type="text/javascript">
var silverlightCtrl = null;
function pluginLoaded(sender, args) {
silverlightCtrl = sender.getHost();
}
function JS_GetFilePath() {
document.getElementById("my_file_element").click();
}
function sendPathToSL() {
var element = document.getElementById("my_file_element");
silverlightCtrl.Content.SL2JS.SL_SetFilePath(element.value);
}
</script>
Then this to the Silverlight object element:
<param name="onLoad" value="pluginLoaded" />
And finally this on the bottom of the body element:
<form enctype="multipart/form-data"
method="post" style="visibility:hidden;
height:0px; width:0px; border:0px; overflow:hidden">
<input id="my_file_element" type="file"
name="file_1" onchange="sendPathToSL();">
</form>
2. Edit C# Class
What we need to do now is, in order:
- Register class for listen to JavaScript events
- Invoke the
JS_GetFilePath
method
- Wait for the answer
1. Register class as listener by adding this row in the constructor:
HtmlPage.RegisterScriptableObject("SL2JS", this);
2. Invoke JavaScript method with:
System.Windows.Browser.HtmlPage.Window.Invoke("JS_GetFilePath");
3. Wait for answer in the method:
[ScriptableMember]
public void SL_SetFilePath(string path)
{
Txt_Path.Text = path;
}
NOTE: Remember to mark this method with [ScriptableMember]
tag!