This is Working solution for

Using SSIS VS 2005 Package In VS 2008 With C# 3.5

Microsoft.SqlServer.Dts.Runtime.Wrapper.ApplicationClass app = new Microsoft.SqlServer.Dts.Runtime.Wrapper.ApplicationClass();

string packagePath=@"C:\Paramount\Internal Projects\TestSSISPackage\TestSSISPackage\bin\Package.dtsx";

Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSPackage90 package = app.LoadPackage(packagePath, true, null);

package.Execute();

🙂