Simple Azure Storage Connection String Parser

readme.md

At time of writing (May 2021), the latest Azure.Storage.Blobs package doesn't seem to have a convenience class for parsing Azure Storage Account connection strings.

This Gist contains a simple class to parse values from connection strings which is based on this SO answer from Partick Mcavy.

There is an example of usage that creates a SAS access URL for a blob (my original use case behind this!) which takes inspriation from Deeksha Gupta's answer here.

AzureStorageConnectionStringParser.cs

using System;
using System.Collections.Generic;

/// <summary> Based on Patric Macvey's answer here https://stackoverflow.com/a/60998564/2608 </summary>
public class AzureStorageConnectionStringParser
{
    readonly Dictionary<string, string> _values = new Dictionary<string, string>();
    readonly string                     _connectionString;

    public AzureStorageConnectionStringParser(string connectionString)
    {
        _connectionString = connectionString;
        foreach (var item in _connectionString.Split(';').Where(x => !string.IsNullOrWhiteSpace(x)))
        {
            var (key, value) = SplitAtFirstEquals(item);
            _values.Add(key, value);
        }
    }

    public string ConnectionString => _connectionString;
    public string AccountName      => ValueOrDefault("AccountName");
    public string AccountKey       => ValueOrDefault("AccountKey");
    public string BlobEndpoint     => ValueOrDefault("BlobEndpoint");
    public Uri    BlobEndpointUri  => new Uri(BlobEndpoint);

    private string ValueOrDefault(string key) => _values.TryGetValue(key, out var value) ? value : default;

    private (string key, string value) SplitAtFirstEquals(string s)
    {
        var index = s.IndexOf('=');
        var key   = s.Substring(0,         index);
        var value = s.Substring(index + 1, s.Length - index - 1);
        return (key, value);
    }
}

Example.cs

/// <summary>
/// This shows an example of use of the AzureStorageConnectionStringParser and also how to construct a SAS access URL for a blob.
/// </summary>
public class SomeClass
{
  private ConnectionString { get; }
  private ContainerName { get; }
  
  /// <summary>
  /// Inspriation taken from Deeksha Gupta's answer here: https://github.com/Azure/azure-storage-net/issues/895#issuecomment-843038602
  /// </summary>
  public string GeneratePreSignedURLAzure(string containerName, string blobName, int timeInMinutes = 15, string storedPolicyName = null)
  {
      var connectionString = new AzureStorageConnectionStringParser(ConnectionString);
      StorageSharedKeyCredential sharedKeyCredential = new StorageSharedKeyCredential(connectionString.AccountName, connectionString.AccountKey);

      var sasBuilder = new BlobSasBuilder()
      {
          BlobContainerName = containerName,
          BlobName          = blobName,
          Resource          = "b",
      };

      if (storedPolicyName == null)
      {
          sasBuilder.StartsOn  = DateTimeOffset.UtcNow.AddMinutes(-5); // Allow for clock differences between the client and the server.
          sasBuilder.ExpiresOn = DateTimeOffset.UtcNow.AddMinutes(timeInMinutes);
          sasBuilder.SetPermissions(BlobContainerSasPermissions.Read);
      }
      else
      {
          sasBuilder.Identifier = storedPolicyName;
      }

      var sasToken = sasBuilder.ToSasQueryParameters(sharedKeyCredential);
      return new Uri($"{connectionString.BlobEndpointUri}{ContainerName}/{blobName}?{sasToken}");
  }  
}