DbContextExtensions

DbContextExtensions.cs

public static class DbContextExtensions
{
    public static string GetMigrationHistoryModel(this DbContext dbContext)
    {
        var modelBase64 = dbContext.Database.SqlQuery<string>(@"
                        DECLARE @binaryContent VARBINARY(MAX);
                        SELECT @binaryContent = Model FROM [__MigrationHistory];
                        SELECT CAST('' AS XML).value( 'xs:base64Binary(sql:variable(''@binaryContent''))', 'varchar(max)' ) AS base64Content;"
                ).FirstOrDefault();

        if (modelBase64 == null) return string.Empty;
        var bytes = Convert.FromBase64String(modelBase64);
        var uncompressed = Decompress(bytes);
        return Encoding.UTF8.GetString(uncompressed);
    }

    private static byte[] Decompress(byte[] gzip)
    {
        using (var stream = new GZipStream(new MemoryStream(gzip), CompressionMode.Decompress))
        {
            const int size = 4096;
            var buffer = new byte[size];

            using (var memory = new MemoryStream())
            {
                int count;
                do
                {
                    count = stream.Read(buffer, 0, size);
                    if (count > 0)
                    {
                        memory.Write(buffer, 0, count);
                    }
                }

                while (count > 0);
                return memory.ToArray();
            }
        }
    }
}