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The SpeedLink .NET client assembly (NETSpeedLinkClient.dll) is built against GridServer SP2 .NET driver (GridServerNETClient.dll - version 5.0.0.48). When you use a newer GridServerNETClient.dll for example version 5.0.50, to run a SpeedLink driver, you must configure your application executable to use the new library. To do this provide an executable config file config.exe which includes these instructions to redirect the binding from the default:

&ltassemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
&ltdependentAssembly>
&ltassemblyIdentity name="GridServerNETClient" publicKeyToken="42129437978483df" />
&ltbindingRedirect oldVersion="5.0.0.48" newVersion="5.0.0.50" />
</dependentAssembly>
</assemblyBinding>

Make sure the oldVersion and newVersion values match the assembly versions used in your environment.
For more information on assembly versioning, please refer to Microsoft MSDN documentation regarding assembly version policies.