Today when I tried to open MS CRM 4.0 plugin registration tool in VS 2010, as usual it asked me upgrade the solution and when I opened after upgrade, after adding web reference I tried to build project and I got below error
Error 1 The type or namespace name ‘Workflow’ does not exist in the namespace ‘System’ (are you missing an assembly reference?) C:\Users\Vikram\Desktop\pluginregistration\AssemblyReader.cs 75 43 pluginregistrationtool
Then I checked .net version in project properties, and it was .net 2.0, so I changed .net version to 3.0 and it worked like a charm.
Hope it will help somebody !!!