Integrating Visio with SharePoint - Visio Services Quick Guide - page 94

Make sure that the following are correct to avoid the error shown in Figure 4-71 :
Figure 4-71. External data connection refresh error
Assembly details are accurate when you add the custom data providers in the
Central Administration.
The wCF services are properly hosted and can communicate with the Custom Data
Providers.
Your configuration files (web.config) have the right binding settings for the wCF.
As discussed earlier, you might encounter the double-hop issue while connecting to
data sources via wCF. If so, you might need to set the credentials under the Secure
Store Service.
Understanding the Custom Data Provider Code
This section provides some more details on the code listings given earlier.
uspGetServerDetails Stored Procedure (Listing 4-2)
This stored procedure contains a simple T-SQL statement that retrieves all rows of data
from the table tblServerStatus .
SELECT ServerName, ServerIP, ServerStatus from tblServerStatus
WCF Service Library (and Interface) Class
(Listings 4-3 and 4-4):
Consider this a data access layer class that would call the uspGetServerDetails stored
procedure and return the output as a data table.