How to retrieve Secret from Azure Key Vault using DefaultAzureCredential

I have setup my keyVault in Azure, and add the secret there. I am now following instructions from Microsoft located here.

My current code looks like below:

            var keyVaultName = Environment.GetEnvironmentVariable("KEY_VAULT_NAME");
            var kvUri = "https://" + keyVaultName + "vault.azure.net";
            var client = new SecretClient(new Uri(kvUri), new DefaultAzureCredential());
            var secret = (await client.GetSecretAsync("my-secret-key")).Value.Value;

I already set up the environment variable (system setting) to hold the name of the key vault with the variable name KEY_VAULT_NAME.

With the code above I am getting a exceptions: The requested name is valid, but no data of the requested type was found

I have a feeling I am using DefaultAzureCredential wrongly and that there is something I am missing?

Solution

I ended up using this resource by Microsoft, which uses virtually identical code but also has details on setting up a managed identity for your web app and giving it access to the specific Key Vault.

The code in my question is also now working having set up that managed identity access.