System.MissingMethodException: Cannot dynamically create an instance of type 'Renci.SshNet.Security.KeyExchangeECCurve25519'. Reason: No parameterless constructor defined.

[Zero-Xiong]

Hi guys, what's the root cause?

Version: 2020.0.2

System.MissingMethodException: Cannot dynamically create an instance of type 'Renci.SshNet.Security.KeyExchangeECCurve25519'. Reason: No parameterless constructor defined.
at Renci.SshNet.Session.WaitOnHandle(WaitHandle, TimeSpan)
at Renci.SshNet.Session.Connect()
at Renci.SshNet.BaseClient.CreateAndConnectSession()

[Rob-Hague]

Are you trimming your application?

[emetlashevskiy]

I have some error, how resolve it?
On win64 work fine, but on linux:
System.MissingMethodException: Cannot dynamically create an instance of type 'Renci.SshNet.Security.KeyExchangeECCurve25519'. Reason: No parameterless constructor defined.
at Renci.SshNet.Session.WaitOnHandle

[emetlashevskiy]

Yes, if untrimmed app when work fine!
You need set "PublishTrimmed" to false, or remove from *.csproj.

[emetlashevskiy]

Another problem, how disable trimming my app if PublishAOT is true?
I tryed

<PackageReference Include="SSH.NET" Version="2020.0.2">
    <IsTrimmable>false</IsTrimmable>
</PackageReference>

but no effect.

[Rob-Hague]

I don't know a lot about trimming. I think you may try "rooting" the assembly as described at this link

https://learn.microsoft.com/dotnet/core/deploying/trimming/trimming-options?pivots=dotnet-7-0#root-assemblies

(untested)

<ItemGroup>
  <TrimmerRootAssembly Include="Renci.SshNet" />
</ItemGroup>

You could even try using "descriptors" to preserve just the specific types listed here:

SSH.NET/src/Renci.SshNet/ConnectionInfo.cs

Lines 344 to 357 in 004b57a

	KeyExchangeAlgorithms = new Dictionary<string, Type>
	{
	{ "curve25519-sha256", typeof(KeyExchangeECCurve25519) },
	{ "[email protected]", typeof(KeyExchangeECCurve25519) },
	{ "ecdh-sha2-nistp256", typeof(KeyExchangeECDH256) },
	{ "ecdh-sha2-nistp384", typeof(KeyExchangeECDH384) },
	{ "ecdh-sha2-nistp521", typeof(KeyExchangeECDH521) },
	{ "diffie-hellman-group-exchange-sha256", typeof(KeyExchangeDiffieHellmanGroupExchangeSha256) },
	{ "diffie-hellman-group-exchange-sha1", typeof(KeyExchangeDiffieHellmanGroupExchangeSha1) },
	{ "diffie-hellman-group16-sha512", typeof(KeyExchangeDiffieHellmanGroup16Sha512) },
	{ "diffie-hellman-group14-sha256", typeof(KeyExchangeDiffieHellmanGroup14Sha256) },
	{ "diffie-hellman-group14-sha1", typeof(KeyExchangeDiffieHellmanGroup14Sha1) },
	{ "diffie-hellman-group1-sha1", typeof(KeyExchangeDiffieHellmanGroup1Sha1) },
	};

---

I can't see a way on the library side to mark it as incompatible with trimming, short of fixing the actual problem which is the use of reflection here:

SSH.NET/src/Renci.SshNet/ServiceFactory.cs

Line 93 in 004b57a

public IKeyExchange CreateKeyExchange(IDictionary<string, Type> clientAlgorithms, string[] serverAlgorithms)

It would probably be fixed by changing ConnectionInfo.KeyExchangeAlgorithms to Dictionary<string, Func<IKeyExchange>> instead of Dictionary<string, Type>

[Zero-Xiong]

PublishTrimmed

Thanks for comment!