For a project and example on how to and use CR Parameters see the Document ( soon to be converted into a Blog )
PS - Removed link to archived SCN post, can no longer update the application and attach it.
PSS - Also remove WIKI link since they too are going away
Crystal Reports for Visual Studio
See Document for more info and sample application (2) is the latest version
Crystal Reports, Parameters, how to, .net , KBA , BI-DEV-NET , BI Software Development Kits (SDKs) - .NET or Other , How To