When we started our move from WCF to gRPC, among the first problems we had to solve was how we can share message types between contracts in different independent services living in separate repositories.
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Moving from WCF to gRPC
As part of migrating a fairly large (for our team size) code base into modern technologies, moving away from WCF as our internal communications protocol was essential, as WCF is not supported in modern .NET (.NET Core, if you like).