Delpoy NetCore application using Azure DevOps - .net-core

Question

I create release pipeline on Azure DevOps server and i have a some problem.
How i can change properties in .net core configuration file (appsettings.EnvName.json).
When I create application on framework I had parameters.xml where I set XPath to value, default value and property name. And on pipeline I set key-value. But on net core app this method don't work =)
I want to use about the same approach. What would I indicate the path to the value and its value. For example:
ConnectionStrings.Db1="Server={DB1.Server};Database={DB1.DbName};Trusted_Connection = True;"
ConnectionStrings.Db2="Server={DB2.Server};Database={DB2.DbName};Trusted_Connection = True;"
Now I have added a step to execute an arbitrary powershell script on a remote server
$jsonFile = 'appsettings.Template.json'
$jsonFileOut = 'appsettings.Production.json'
$configValues =
'ConnectionStrings.Db1="Server={DB1.Server};Database={DB1.DbName};Trusted_Connection = True;"',
'ConnectionStrings.Db2="Server={DB2.Server};Database={DB2.DbName};Trusted_Connection = True;"'
$config = Get-Content -Path $jsonFile | ConvertFrom-Json
ForEach ($item in $configValues)
{
$kv = $item -split "="
Invoke-Expression $('$config.' + $kv[0] + '="' + $kv[1] + '"')
}
$config | ConvertTo-Json | Out-File $jsonFileOut
But I don’t really like this solution, how can I do the same in a more beautiful way

Answer 1

dotnet core handles this in a different way. Full framework based on app.config transformation. It means that you defined one file which later was trasnformed for given build configuration (like Debug, Release, or your own). In dotnet core you define appsettings.json for each environment. This works very well because all settings are in your compiled app. And then at runtime bases on ASPNETCORE_ENVIRONMENT environment variable a proper settings is selected. Thus you may have one package for your all environments without recompilation. To benefit from that you must define file per each enviroment, but this is not transformation. This is full file.
For instance file for your local development may look like this:
{
"ConnectionStrings": {
"BloggingDatabase": "Server=(localdb)\\mssqllocaldb;Database=EFGetStarted.ConsoleApp.NewDb;Trusted_Connection=True;"
},
}
And file for your dev enviroment appsettings.dev.json like this:
{
"ConnectionStrings": {
"BloggingDatabase": "Server=102.10.10.12\\mssqllocaldb;Database=EFGetStarted.ConsoleApp.NewDb;Trusted_Connection=True;"
},
}
And then to configure loading this file you have to have configured Startup method:
public Startup(IHostingEnvironment env)
{
var builder = new ConfigurationBuilder()
.SetBasePath(env.ContentRootPath)
.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
.AddEnvironmentVariables();
this.Configuration = builder.Build();
}
This will load all your appsettings file and later use proper file based on enviroment variable.
To set this variable you may use this command in command prompt setx ASPNETCORE_ENVIRONMENT Dev or this in Powershell [Environment]::SetEnvironmentVariable("ASPNETCORE_ENVIRONMENT", "Dev", "Machine")
I hope it help you understand how settings works on dotnet core. If you need more guidance please check this links:
Configuration in ASP.NET Core
Use multiple environments in ASP.NET Core
To sum up you don't need to change your settings in release pipeline. You need to preapre full file per enviromnet where you are going to host your app. You can be interested in replacing some values in file based on variables in your pipeline. You can consider few options here like
token replacement
JSON variable substitution example
This is usefult when you don't want to keep your secrets directly in source code.
EDIT
If you want to replace values in you appsettings file one of the option is token replace. For this you must first instead of values keep token in your file. For instance #{SomeVariable}# will be replaced with value of SomeVariable` from your pipeline for this confirguration of token replace task.