SqlServer将XML转换为varbinary并在.NET中解析它（C＃）(SqlServer Converting XML to varbinary and parsing it in .NET (C#))

 请考虑以下代码： 
 
[Test]
    public void StackOverflowQuestionTest()
    {
        const string connectionString = "enter your connection string if you wanna test this code";

        byte[] result = null;
        using (var connection = new SqlConnection(connectionString))
        {
            connection.Open();
            using (var sqlCommand = new SqlCommand("declare @xml as xml = '<xml/>' SELECT convert(varbinary(max), @xml) as value"))
            //using (var sqlCommand = new SqlCommand("SELECT convert(varbinary(max), N'<xml/>') as value"))
            {
                sqlCommand.Connection = connection;

                using (SqlDataReader reader = sqlCommand.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        result = (byte[])reader["value"];
                    }

                    reader.Close();
                }
            }
        }

        string decodedString = new UnicodeEncoding(false, true).GetString(result);
        var document = XElement.Parse(decodedString);
    }
 
 如果我运行此测试，我会收到一条消息的XmlException：“根级别的数据无效。第1行，位置1”。 事实证明问题是“0xFFFE”前导码，它被认为是无效字符。 请注意，如果我使用注释字符串，一切都很好，这对我来说很奇怪。 看起来SqlServer在UCS-2中存储带有BOM的XML字符串，同时它存储没有它的nvarchar值。 主要问题是：如何将此字节数组解码为不包含此前导码（BOM）的字符串？ 

Consider the following code:
 
[Test]
    public void StackOverflowQuestionTest()
    {
        const string connectionString = "enter your connection string if you wanna test this code";

        byte[] result = null;
        using (var connection = new SqlConnection(connectionString))
        {
            connection.Open();
            using (var sqlCommand = new SqlCommand("declare @xml as xml = '<xml/>' SELECT convert(varbinary(max), @xml) as value"))
            //using (var sqlCommand = new SqlCommand("SELECT convert(varbinary(max), N'<xml/>') as value"))
            {
                sqlCommand.Connection = connection;

                using (SqlDataReader reader = sqlCommand.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        result = (byte[])reader["value"];
                    }

                    reader.Close();
                }
            }
        }

        string decodedString = new UnicodeEncoding(false, true).GetString(result);
        var document = XElement.Parse(decodedString);
    }
 
If I run this test I get an XmlException with message : "Data at the root level is invalid. Line 1, position 1." As it turns out the problem is "0xFFFE" preamble which is considered as invalid character. Note that if I use commented string instead, everything works just fine, which is strange as per me. Looks like SqlServer stores XML strings in UCS-2 with a BOM, and at the same time it stores nvarchar values without it. The main question is: how can I decode this byte array to string which will not contain this preamble (BOM)?

原文：https://stackoverflow.com/questions/13014709