Azure Cloud Service Role Instance Logging to Azure Table Storage

Main logic is in WebRole1/TableLog.cs.

Write to Table Storage

Get started with Azure Table storage and the Azure Cosmos DB Table API using .NET: https://docs.microsoft.com/en-us/azure/cosmos-db/table-storage-how-to-use-dotnet

Need to install packages:

• Microsoft.Azure.Storage.Common, with version less than or equal to 9.0.0.1 (<= 9.0.0.1).
• Microsoft.Azure.CosmosDB.Table

Cloud Service Setup

<role name>.dll.config must be added to the Role project to avoid assembly referencing issue.

It should contain assembly redirections. You may simply copy them from web.config.

<?xml version="1.0" encoding="utf-8"?>

<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Azure.Storage.Common" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-9.0.0.0" newVersion="9.0.0.0" />
      </dependentAssembly>
      ...
    </assemblyBinding>
  </runtime>
</configuration>

Otherwise, you may received error

Could not load file or assembly 'Microsoft.Azure.Storage.Common, Version=8.6.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

This is because Microsoft.Azure.CosmosDB.Table internally uses Microsoft.Azure.Storage.Common 8.6.0.0.

https://blogs.msdn.microsoft.com/cie/2015/09/06/cloud-services-roles-recycling-with-the-error-system-io-fileloadexception-could-not-load-file-or-assembly/

"However, in Azure Cloud Services, the assembly bindings from web.config and app.config does not have effect, due to the fact that WaIISHost (Web Role) and WaWorkerHost (Worker Role) are not able to read these two configuration files, instead, they read the <role name>.dll.config file, and this is the file where the assembly binding configuration need to be. Please, refer to this article for more details.

The problem is, the <role name>.dll.config file is not added to Solution by default, and even if it is there, it may happen that it does not have the assembly binding configuration like in web.config or app.config."

Another weird effect is that if <role name>.dll.config is not added to the project with Copy to Output Directory set to Copy Always, it is still generated as a duplicate of web.config in the Role's bin folder, but never packaged to cspkg. Don't know why. https://stackoverflow.com/questions/25553010/why-doesnt-mywebsite-dll-config-get-included-in-my-cspkg#comment55405844_25563008

Make sure the role has elevated permission in order to write log to C:\log.txt.

<?xml version="1.0" encoding="utf-8"?>

<ServiceDefinition name="cs_log" xmlns="http://schemas.microsoft.com/ServiceHosting/2008/10/ServiceDefinition" schemaVersion="2015-04.2.6">
  <WebRole name="WebRole1" vmsize="Medium">
    <Runtime executionContext="elevated" />
    ...
  </WebRole>
</ServiceDefinition>

Result

View Table in Storage Explorer.

RDP into the instance and check C:\log.txt.