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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Collections;
using System.Collections.Generic;
namespace Microsoft.Extensions.Configuration.EnvironmentVariables
{
/// <summary>
/// Provides configuration key-value pairs that are obtained from environment variables.
/// </summary>
public class EnvironmentVariablesConfigurationProvider : ConfigurationProvider
{
// Connection string prefixes for various services. These prefixes are used to identify connection strings in environment variables.
// az webapp config connection-string set: https://learn.microsoft.com/en-us/cli/azure/webapp/config/connection-string?view=azure-cli-latest#az-webapp-config-connection-string-set
// Environment variables and app settings in Azure App Service: https://learn.microsoft.com/en-us/azure/app-service/reference-app-settings?tabs=kudu%2Cdotnet#variable-prefixes
private const string MySqlServerPrefix = "MYSQLCONNSTR_";
private const string SqlAzureServerPrefix = "SQLAZURECONNSTR_";
private const string SqlServerPrefix = "SQLCONNSTR_";
private const string CustomConnectionStringPrefix = "CUSTOMCONNSTR_";
private const string PostgreSqlServerPrefix = "POSTGRESQLCONNSTR_";
private const string ApiHubPrefix = "APIHUBCONNSTR_";
private const string DocDbPrefix = "DOCDBCONNSTR_";
private const string EventHubPrefix = "EVENTHUBCONNSTR_";
private const string NotificationHubPrefix = "NOTIFICATIONHUBCONNSTR_";
private const string RedisCachePrefix = "REDISCACHECONNSTR_";
private const string ServiceBusPrefix = "SERVICEBUSCONNSTR_";
private readonly string _prefix;
private readonly string _normalizedPrefix;
/// <summary>
/// Initializes a new instance.
/// </summary>
public EnvironmentVariablesConfigurationProvider()
{
_prefix = string.Empty;
_normalizedPrefix = string.Empty;
}
/// <summary>
/// Initializes a new instance with the specified prefix.
/// </summary>
/// <param name="prefix">A prefix used to filter the environment variables.</param>
public EnvironmentVariablesConfigurationProvider(string? prefix)
{
_prefix = prefix ?? string.Empty;
_normalizedPrefix = Normalize(_prefix);
}
/// <summary>
/// Loads the environment variables.
/// </summary>
public override void Load() =>
Load(Environment.GetEnvironmentVariables());
/// <summary>
/// Generates a string representing this provider name and relevant details.
/// </summary>
/// <returns>The configuration name.</returns>
public override string ToString()
{
string s = GetType().Name;
if (!string.IsNullOrEmpty(_prefix))
{
s += $" Prefix: '{_prefix}'";
}
return s;
}
internal void Load(IDictionary envVariables)
{
var data = new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase);
IDictionaryEnumerator e = envVariables.GetEnumerator();
try
{
while (e.MoveNext())
{
string key = (string)e.Entry.Key;
string? value = (string?)e.Entry.Value;
if (key.StartsWith(MySqlServerPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, MySqlServerPrefix, "MySql.Data.MySqlClient", key, value);
}
else if (key.StartsWith(SqlAzureServerPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, SqlAzureServerPrefix, "System.Data.SqlClient", key, value);
}
else if (key.StartsWith(SqlServerPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, SqlServerPrefix, "System.Data.SqlClient", key, value);
}
else if (key.StartsWith(PostgreSqlServerPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, PostgreSqlServerPrefix, "Npgsql", key, value);
}
else if (key.StartsWith(ApiHubPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, ApiHubPrefix, null, key, value);
}
else if (key.StartsWith(DocDbPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, DocDbPrefix, null, key, value);
}
else if (key.StartsWith(EventHubPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, EventHubPrefix, null, key, value);
}
else if (key.StartsWith(NotificationHubPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, NotificationHubPrefix, null, key, value);
}
else if (key.StartsWith(RedisCachePrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, RedisCachePrefix, null, key, value);
}
else if (key.StartsWith(ServiceBusPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, ServiceBusPrefix, null, key, value);
}
else if (key.StartsWith(CustomConnectionStringPrefix, StringComparison.OrdinalIgnoreCase))
{
HandleMatchedConnectionStringPrefix(data, CustomConnectionStringPrefix, null, key, value);
}
else
{
AddIfNormalizedKeyMatchesPrefix(data, Normalize(key), value);
}
}
}
finally
{
(e as IDisposable)?.Dispose();
}
Data = data;
}
private void HandleMatchedConnectionStringPrefix(Dictionary<string, string?> data, string connectionStringPrefix, string? provider, string fullKey, string? value)
{
string normalizedKeyWithoutConnectionStringPrefix = Normalize(fullKey.Substring(connectionStringPrefix.Length));
// Add the key-value pair for connection string, and optionally provider name
AddIfNormalizedKeyMatchesPrefix(data, $"ConnectionStrings:{normalizedKeyWithoutConnectionStringPrefix}", value);
if (provider != null)
{
AddIfNormalizedKeyMatchesPrefix(data, $"ConnectionStrings:{normalizedKeyWithoutConnectionStringPrefix}_ProviderName", provider);
}
}
private void AddIfNormalizedKeyMatchesPrefix(Dictionary<string, string?> data, string normalizedKey, string? value)
{
if (normalizedKey.StartsWith(_normalizedPrefix, StringComparison.OrdinalIgnoreCase))
{
data[normalizedKey.Substring(_normalizedPrefix.Length)] = value;
}
}
private static string Normalize(string key) => key.Replace("__", ConfigurationPath.KeyDelimiter);
}
}
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