SharePoint Designer 2013: an error occurred while trying to fetch data from your sharepoint

Whilst try to open a SharePoint 2013 site with SP Designer 2013 I received this error: "an error occurred while trying to fetch data from your SharePoint site".

A Google search returned nothing but results for similar issues with SP Designer 2010. Many of the posts (like this one) I found suggested the solution had to do with windows authentication, but none of solution matched with what I saw in windows IIS in Windows 2008 SP2.

There is a private joke among the help desk support guys that I have worked with: "Shut up and reboot" Which is the crude way of saying sometimes the only thing you can do is restart, and many times, as in this time, it works. The solution, In IIS, disabled then re-enabled Windows Authentication in on the SharePoint - 80 Site.

Let me walk you through it:

In Windows Server 2008:
1) Open IIS.
2) Click on "SharePoint - 80"
3) Double-click the Authentication icon.
4) Right Click "Windows Authentication".
5) Click Disable.

4) Right Click "Windows Authentication".
5) Click Enable.

Hopefully, you will no longer receive the error when trying to open a site in SharePoint Designer 2013.

Lookup Selected boxes: how to get "is empty" or "is not empty"

Whilst using SharePoint Designer to create a workflow I needed a way to check if a lookup column value was 'blank' or 'not blank'. This is not possible with Lookup type columns, but annoyingly and confusingly it is possible with other data types.

Figure 1

SharePoint only provides two operator options on lookup columns "Equal" or "not Equals". The problem is SP Designer will not allow you to simply enter a comparison value of "" or "blank" or "null".

This trick is to convert your Lookup value into a different data type, a string variable.
 
Example: I have a List containing a column called Projects, which is a lookup to another List (of projects info).
 

Figure 2

As you can see in Figure 2: First put your lookup value into a string variable.

Then use the string in your 'if' statement. You can now check if you value 'is empty' or 'is not empty'.