MissingMethodException - Serilog.LoggerConfiguration Serilog.SeqLoggerConfigurationExtensions.Seq()

I’m getting this exception when starting up my Azure Function App locally from Visual Studio:

System.MissingMethodException: 'Method not found: 'Serilog.LoggerConfiguration Serilog.SeqLoggerConfigurationExtensions.Seq(Serilog.Configuration.LoggerSinkConfiguration, System.String, Serilog.Events.LogEventLevel, Int32, System.Nullable`1<System.TimeSpan>, System.String, System.String, System.Nullable`1<Int64>, System.Nullable`1<Int64>, Serilog.Core.LoggingLevelSwitch, System.Net.Http.HttpMessageHandler, System.Nullable`1<Int64>, Boolean, Int32)'.

My LoggerConfiguration is:

var environmentName = CloudConfigurationManager.GetSetting("Environment") ?? "Local";
var seqPath = CloudConfigurationManager.GetSetting("SeqPath") ?? "http://localhost:5341/";
var seqApiKey = CloudConfigurationManager.GetSetting("SeqApiKey") ?? "";
var levelSwitch = new LoggingLevelSwitch();

var loggerConfiguration = new LoggerConfiguration()
    .WriteTo.Seq(seqPath, apiKey: seqApiKey, controlLevelSwitch: levelSwitch)
    .WriteTo.TraceWriter(traceWriter)
    .MinimumLevel.ControlledBy(levelSwitch)
    .Enrich.WithProperty("Environment", environmentName);

If I remove this line, the problem goes away:

.WriteTo.Seq(seqPath, apiKey: seqApiKey, controlLevelSwitch: levelSwitch)

I’m using…

• Visual Studio 15.3.0 Preview 2.0 (required for the Azure Functions tooling)
• .NET Framework 4.6.2
• Any CPU
• Conditional compilation symbols: NET462
• The following packages:

    <PackageReference Include="Microsoft.Azure.WebJobs" Version="2.1.0-beta1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions" Version="2.1.0-beta1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.Http" Version="1.0.0-beta1" />
    <PackageReference Include="Microsoft.Azure.WebJobs.ServiceBus" Version="2.1.0-beta1" />
    <PackageReference Include="Microsoft.WindowsAzure.ConfigurationManager" Version="3.2.3" />
    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="1.0.0-alpha3" />
    <PackageReference Include="Serilog" Version="2.4.0" />
    <PackageReference Include="Serilog.Sinks.AzureWebJobsTraceWriter" Version="1.0.20" />
    <PackageReference Include="Serilog.Sinks.Seq" Version="3.3.1" />

[tjrobinson]

Right, I’ve made some progress. This reproduces the issue:

https://github.com/tjrobinson/SerilogSeqIssue70

Removing the reference to System.Net.Http 4.3.2 fixes it!

Unfortunately that’s not possible in my real usage but it’s a clue.

[vishal-bold]

Hi Tom,

I didn’t install Azure Functions runtime on this machine, but got the System.Net.Http related error to repro by referencing output binaries from a separate console app.

In my case, I was able to get rid of the error by running:

install-package system.net.http -Version 4.3.2

in the consuming app. I’m not sure whether doing this from the Azure Function project itself will help, but it might be worth a try.

(This SO answer makes me think we could be hitting a limitation of the platform: https://stackoverflow.com/a/38101488/138206.)

This solution solved my problem. I had different vesion of system.net.http.