C# check for sql server errors

Question

I am working on a C#.net 2008 desktop application where code has been added to verify if a user has access to various parts of a desktop application based upon the tab they select. The C#.net 2008 desktop, code has been added to verify if a user has access to various parts of the application. The user will only see the parts of the desktop they should have access to or a error message will be displayed right away saying 'you do not have access, contact network administrator'.

There has been code added to sql server 2008 r2 also that checks to see if the user has access based upon the groups they are assigned to in sql server.

Current problem. When the user tries to access the sql server r2 database through the application, a runtime error is displayed shwoing the user does not have access (basically to sql server).

Thus to display a user friendly message and close out of the applicartion, I would likec to know what my options are.

Thus let me know if I can do any of the following:

1. Is there some code the .net desktop can access before the first call to sql server to see if the user has access based upon how sql server accesses the ldap code? If so, can you tell me and/or point me to a reference I can use to include in my code?

2. Is there some code the .net desktop can access before all calsl to sql server to see if the user has access based upon how sql server accesses the ldap code? If so, can you tell me and/or point me to a reference I can use to include in my code?

3. If there is no .net code to check prior to the call, what kind of logic can I put in a try catch block to capture the error? What kind of an error would I be getting that I need to check for? What is the exception type, error code, error code number, and/or error message that I should be checking for? Would you display come sample code and/or point me to a url that I can use as a reference?