Adventures in Consulting

Solving the “User cannot be found” error with SPFile.Author

Valdon — Thu, 16 Jun 2011 09:05:00 GMT

I ran into a bug today that was a bit unusual. We have a custom ASP.NET page that shows information from a custom list in SharePoint 2007. That page shows details, including the Author, for attachments. On one particular list item, users started getting a “User cannot be found” error whey they tried to view it with our custom page. The stack trace showed that it was getting the error in Microsoft.SharePoint.SPFile.get_Author().

It turns out that SPFile stores the user as a login name and tries to resolve the name using SPWeb.SiteUsers, which throws an error if the login name is not found. The issue was, in this case, the attachment author had been removed from Active Directory and was no longer in SharePoint’s user list, hence the error.

The fix is to go directly to the SPFile properties and get the login name. Since we can no longer resolve the login name to a user display name, we just display the login name.

string GetAuthorName(SPFile file)
{
    SPUser author = null;
    try { author = file.Author; } catch { }
    return (author == null) ? (string)file.Properties["vti_author"] : author.Name;
}

Remove List Item Menu Options with Javascript

Valdon — Tue, 08 Jun 2010 12:03:37 GMT

SharePoint has a lot of JavaScript code to manage UI, and a lot of customization can be done by modifying out-of-box JavaScript. However, modifying system files is not a good idea. Instead, you usually will want to copy the file and make your custom changes there.

One other way to make customizations is to “override” functions using pointers. In our case, we didn’t want the “Manage Permissions” options to show up in the list item menu for most users. Just removing the “Manage Permissions” permission for those user groups didn’t work because they also have the “Enumerate Permissions” permission, which is needed for general access to the list. The “Manage Permissions” menu option shows up for either of these.

So, there is a handy function called AddManagePermsMenuItem in the core.js file that you can “override”. In this example, I’m checking to see if the user has “Manage Permission” permission (0x20000000 bit is set):

    var original_AddManagePermsMenuItem = AddManagePermsMenuItem;
    AddManagePermsMenuItem = function(m, ctx, listId, url) {
        if (!HasRights(0x0, 0x2000000))
            return;
        original_AddManagePermsMenuItem(m, ctx, listId, url);
    }

First it saves a pointer to the current function, then replaces the function with an anonymous function. The anonymous function checks the rights and returns if the user doesn’t have “Manage Permission” rights. If the user does, it calls the original AddManagePermsMenuItem through the pointer we saved earlier.

Place this script in your master page after the inclusion of core.js and any list view that uses that master page will no longer show the “Manage Permissions” option for most users.

Customizing ASP.NET Validators without using the CustomValidator Control

Valdon — Thu, 11 Feb 2010 08:32:51 GMT

This isn’t a SharePoint tip, per se, but it is an interesting way to expand on what the default RequiredFieldValidator control does for you.

We already had validation in our custom pages using the RequiredFieldValidator control, and it was working well, however, our customer wanted the behavior to be different than the default of displaying an asterisk next to required fields. Instead, it needed to highlight the required fields by shading them a light red (I think that’s called pink… anyway…). My first thought was to change to use the CustomValidator control, which would allow us to have custom client-side script. However, that would mean that I would need to implement the validation logic in JavaScript for the client and again in C# for the server. The standard RequiredFieldValidator class does both client and server-side validation automatically, which is nice.

So, instead, I remembered that you can mess with function pointers in JavaScript and essentially override whatever functions you want. With a little poking around using IE 8’s developer add-in, I found that the function I wanted to “override” was the ValidatorUpdateDisplay function. Within this function, I could add in the code to highlight the field any way I wanted.

So, here’s what the JavaScript looks like.

var Original_ValidatorUpdateDisplay = ValidatorUpdateDisplay;
ValidatorUpdateDisplay = function(val) {
    Original_ValidatorUpdateDisplay(val);
    var valControl = document.getElementById(val.controltovalidate);
    if (valControl) {
        valControl.style.backgroundColor = val.isvalid ? 0xFFFFFF : 0xFFE0D6;
    }
}

Place this within your