IConfiguration and Azure KeyVault

Question

I have a .NET 8 application where I read in values from an Azure Keyvault and then bind to configuration:

builder.Configuration.AddAzureKeyVault(new Uri($"https://mykeyvault.vault.azure.net/"),
            new DefaultAzureCredential()
        );

I then try and bind this configuration:

builder.Services.Configure<Settings>(builder.Configuration)
    .AddOptionsWithValidateOnStart<Settings>()
    .ValidateDataAnnotations();

In my Settings class, I have a property which is a string array:

public string[] MyArrayProperty { get; set; }

The value in the keyvault is a comma separated list:

"USD,EUR,GBP,CAD,JPY"

When I try and bind this property it is returned as null - I understand that my property is expected a string array and I am passing it a string.

How can I convert this string to an array when the binding process takes place?

Michał Turczyn · Accepted Answer · 2025-08-12 10:28:20Z

0

There's a way to specify array settings in app configuration in ASP.NET Core/Azure Functions.

The way to specify config is (i present two ways):

"ArrayTest": {
  "FlatArray": [ "a", "b", "c" ],
  "Indexed:0": "a",
  "Indexed:1": "b",
  "Indexed:2": "c"
}

Then i tested it by using options pattern:

public class ArrayTest
{
    public string[] FlatArray { get; set; }

    public string[] Indexed { get; set; }
}

then configured it:

builder.Services.Configure<ArrayTest>(builder.Configuration.GetSection("ArrayTest"));

Then i could see both FlatArray and Indexed array filled correctly.

So, in order to do this in Azure Key Vault, you could see the second convention with indexes within the keys:

"Indexed:0": "a",
"Indexed:1": "b",
"Indexed:2": "c"

In order to add new item to array in config, you just add new Indexed:n key with value.

answered Aug 12 at 10:28

Michał Turczyn

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