Is it possible to generate nullable members in protobuf-net?
message ProtoBuf1 {
optional Int32? databit = 1;
optional Nullable databool
Import "wrappers.proto" supports nullable values:
Full list of supported types - https://docs.microsoft.com/en-us/dotnet/architecture/grpc-for-wcf-developers/protobuf-data-types#nullable-types
Example:
syntax = "proto3";
import "google/protobuf/wrappers.proto";
message ProtoPerson {
google.protobuf.StringValue firstName = 1;
google.protobuf.StringValue lastName = 2;
google.protobuf.StringValue address1 = 3;
google.protobuf.Int32Value age = 4;
}
Here's my solution for nullable types when using Google's Protobuf .NET API which requires Protocol Buffers version 3. (Note that this is not using Marc Gravell's protobuf-net, so this isn't an exact answer to the question asked.)
In NullableInt32.proto
:
syntax = "proto3";
message NullableInt32 {
int32 value = 1;
}
In NullableInt32Extensions.cs
:
public static class NullableInt32Extensions
{
public static bool HasValue(this NullableInt32 source)
{
return source != null;
}
}
public partial class NullableInt32
{
public static implicit operator int? (NullableInt32 other)
{
return other == null ? (int?)null : other.Value;
}
public static implicit operator NullableInt32(int? other)
{
return other == null ? null : new NullableInt32 { Value = other.Value };
}
}
This pattern can be used for any of the Protobuf non-length delimited scalar values—double
, float
, int32
, int64
, uint32
, uint64
, sint32
, sint64
, fixed32
, fixed64
, sfixed32
, sfixed64
, and bool
.
Here's how all of this works. Say you have a Record
message that has a NullableInt32
field, and in this contrived example it's the only field.
In Record.proto
:
syntax = "proto3";
import "NullableInt32.proto";
message Record {
NullableInt32 id = 1;
}
Once this is compiled to C# with Google's protoc.exe
, you can treat the Id
property almost exactly like a Nullable<int>
.
var r = new Record();
// r.Id is null by default, but we can still call HasValue()
// because extension methods work on null references.
r.Id.HasValue(); // => false
// We can explicitly set Id to null.
r.Id = null;
// We can set Id to a primitive numeric value directly
// thanks to our implicit conversion operators.
r.Id = 1;
// We can also use NullableInt32 in any context that expects a
// Nullable<int>. The signature of the following method is
// bool Equals(int?, int?).
Nullable.Equals<int>(r.Id, 1); // => true
// We can explicitly set Id to a NullableInt32.
r.Id = new NullableInt32 { Value = 1 };
// Just like Nullable<int>, we can get or set the Value of a
// NullableInt32 directly, but only if it's not null. Otherwise,
// we'll get a NullReferenceException. Use HasValue() to avoid this.
if(r.Id.HasValue())
r.Id.Value.ToString(); // => "1"
// Setting Id to 0 is the same as setting Id to a new
// NullableInt32 since the default value of int32 is 0.
// The following expressions are equivalent.
r.Id = 0;
r.Id = new NullableInt32();
r.Id = new NullableInt32 { Value = 0 };
r.Id.Value = 0; // as long as Id is not null
Finally, let's look at how our Record
message will be transfered over the wire with different values for Id
.
var r = new Record();
// When Id is null, Record is empty since it has no other fields.
// Explicitly setting Id to null will have the same effect as
// never setting it at all.
r.Id = null;
r.ToByteArray(); // => byte[0]
// Since NullableInt32 is a Protobuf message, it's encoded as a
// length delimited type. Setting Id to 1 will yield four bytes.
// The first two indicate the type and length of the NullableInt32
// message, and the last two indicate the type and value held within.
r.Id = 1;
r.ToByteArray(); // => byte[] {
// 0x0a, // field = 1, type = 2 (length delimited)
// 0x02, // length = 2
// 0x08, // field = 1, type = 0 (varint)
// 0x01, // value = 1
// }
// When Id is set to the default int32 value of 0, only two bytes
// are needed since default values are not sent over the wire.
// These two bytes just indicate that an empty NullableInt32 exists.
r.Id = 0;
r.ToByteArray(); // => byte[] {
// 0x0a, // field = 1, type = 2 (length delimited)
// 0x00, // length = 0
// }
Yes, but it doesn't generate them by default if you are doing codegen from .proto.
If this is just C#, of course, you don't need a .proto - just:
[ProtoContract]
public class ProgoBuf1
{
[ProtoMember(1)]
public int? Foo {get;set;}
[ProtoMember(2)]
public float? Bar {get;set;}
}
If you are working from .proto, you could consider copying and editing csharp.xslt
to suit your preferred layout.