System.MissingMethodException for JsonDocument.Parse(System.ReadOnlyMemory`1<Char>, System.Text.Json.JsonDocumentOptions)

[Trivedi-Ashish]

I have a library which depends on below NuGet packages,

• System.Text.Json (NuGet version 8.0.5) which in turn depends on System.Memory (NuGet 4.5.5)
• System.Memory (NuGet version 4.6.3)

The library acts as a plugin to an Application on which I have limited control.
I am supposed to just supply my library (a single DLL) to the application. Application loads my library and all my dependencies either from its own installation path or windows OS location.

I am getting MissingMethodException in my library when it is executed by the application. I am using JsonDocument.Parse method overload which takes in ReadOnlyMemory.

System.MissingMethodException: Method not found: 'System.Text.Json.JsonDocument System.Text.Json.JsonDocument.Parse(System.ReadOnlyMemory`1, System.Text.Json.JsonDocumentOptions)

On investigating the DLLs loaded by the application (using Process Explorer), I found out that application has below DLLs loaded in its memory,

• System.Text.Json.dll (from NuGet 9.0.9)
• System.Memory.ni.dll (native DLL corresponding to managed DLL of version NuGet 4.5.5).

This should have worked. But I got MissingMethodException.

Next, I disabled native image load for System.Memory.ni.dll (assuming native assembly may be causing some conflict). On disabling native image load, application loads managed System.Memory.dll (4.5.5) from its own installation path.

 <disableNativeImageLoad>
  <assemblyIdentity name="System.Memory" />
</disableNativeImageLoad>

I even added System.Memory (NuGet version 4.6.3) in the GAC so that my library may load it if it requires during execution (and in fact it gets loaded, so at a time there are two versions of System.Memory.dll loaded into application memory, one 4.5.5 from its own installation path and another 4.6.3 from GAC)

Now, I don't understand why I am still getting MissingMethodException even after both System.Memory NuGet version 4.5.5 and 4.6.3 are loaded.

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[jilles-sg]

The MissingMethodException is expected if your code uses System.Memory 4.6.3 and System.Text.Json uses System.Memory 4.5.5, since each version of System.Memory defines its own distinct System.ReadOnlyMemory<T> type.

I suggest ensuring both places use the same version of System.Memory, such as by downgrading your own System.Memory dependency or by adding some sort of binding redirect. See
https://learn.microsoft.com/en-us/dotnet/framework/configure-apps/redirect-assembly-versions for more information.

Alternatively, not using System.Memory types between the libraries would work around the issue.