如何从 GZipStream 获取字节数组或可读流

Question

我想将字节数组的压缩版本写入 SQL Server varbinary(max) 列。

我想为 SqlClient 命令的参数提供 SqlBytes 类型，并尝试实例化该类型：

// data is a byte array at this point
SqlParameter p7 = new SqlParameter("@bytes", Compress(data));
p7.SqlDbType = SqlDbType.VarBinary;


public static SqlBytes Compress(byte[] input)
{

    using (MemoryStream memstream = new MemoryStream(input))
    {    
        using (GZipStream zipped = new GZipStream(memstream, CompressionMode.Compress))
        {               
            return new SqlBytes(zipped);    
        }    
    }
}

但命令失败并出现“不支持此操作”错误（请参阅下面的跟踪）。因此，我需要将压缩内容从 GZipStream 中取出并转换为允许实例化 SqlBytes 类型的表单。这是怎么做到的？

注意：GZipStream 不支持读取，因此zipped.CopyTo( myOuputMemoryStream) 将不起作用。

at System.IO.Compression.GZipStream.get_Length()
at System.Data.SqlTypes.SqlBytes.get_Value()
at System.Data.SqlClient.SqlParameter.BinarySize(Object value, Boolean isSqlType)
at System.Data.SqlClient.SqlParameter.GetActualSize()
at System.Data.SqlClient.SqlParameter.ValidateTypeLengths(Boolean yukonOrNewer)
at System.Data.SqlClient.SqlCommand.SetUpRPCParameters(_SqlRPC rpc, Int32 startCount, Boolean inSchema, SqlParameterCollection parameters)
at System.Data.SqlClient.SqlCommand.BuildRPC(Boolean inSchema, SqlParameterCollection parameters, _SqlRPC& rpc)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at .Form1.Save2Database(Byte[] data) 

in c:\\Users\\foo\\Documents\\Visual Studio 2013\\Projects\\Test\\Test\\Form1.cs:line 228

Answer 1

您传递给 GZipStream 构造函数的流是以压缩（或解压缩）格式写入数据的流。您应该创建一个空的内存流并使用 GZipStream 将字节写入其中：

public static SqlBytes Compress(byte[] input)
{

    using (MemoryStream memstream = new MemoryStream())
    {    
        using (GZipStream zipped = new GZipStream(memstream, CompressionMode.Compress))
        {               
            zipped.Write(input, 0, input.Length);
        }   

        return new SqlBytes(memstream);             
    }
}