In our custom property we use the FileManagerBrowser.aspx in a dialog to retreive the path to the selected image.

Here is the code:

function OpenFileDialogLink(url, pageId, parentPageId, folderId, selectedfile, tbClientID) {    url += '?id=' + pageId + '&parent=' + parentPageId + '&folderid=' + folderId;    url += '&browserselectionmode=image&selectedfile=' + selectedfile;    var linkAttributes = new Object();    var dialogArguments = linkAttributes;    var features = { width: 600 };    var callbackArguments = new Object();    callbackArguments.myControlId = tbClientID;    /* opens the filemanagerbrowser dialog */    EPi.CreateDialog(url, OnDialogClosed, callbackArguments, dialogArguments, features);    return false;}
function OnDialogClosed(returnValue, callbackArguments) {    if (returnValue != undefined && returnValue != 0) {
        var myCtrl = document.getElementById(callbackArguments.myControlId);        myCtrl.value = returnValue;        SetPreviewImage(callbackArguments.myControlId);    }}

Calling it with the following code:

btFile.OnClientClick = string.Format("return OpenFileDialogLink('{0}', '{1}', '{2}', '{3}', '{4}', '{5}')",

                    EPiServer.UriSupport.ResolveUrlFromUIBySettings("edit/FileManagerBrowser.aspx"),

                    CurrentPage.PageLink, CurrentPage.ParentLink, pageDirName,

                    System.Web.HttpUtility.UrlEncode(tbFile.Text), tbFile.ClientID);

The problem is that the returnValue parameter is not the selected file's path but instead [object Object]. We are using EPiServer CMS 6. Any help would be very appreciated!