将字符串转换为内存流 - 内存流是不可扩展的？

Question

我试图将字符串写入内存流,但失败并显示错误消息:

Memory stream is not expandable.

产生此问题的代码行:

context.Response.Filter = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(myPage));

有人有解决方法/解决方法吗？

堆栈跟踪:

[NotSupportedException: Memory stream is not expandable.]
   System.IO.MemoryStream.set_Capacity(Int32 value) +9385744
   System.IO.MemoryStream.EnsureCapacity(Int32 value) +50
   System.IO.MemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count) +265
   System.Web.HttpWriter.FilterIntegrated(Boolean finalFiltering, IIS7WorkerRequest wr) +9155697
   System.Web.HttpResponse.FilterOutput() +159
   System.Web.CallFilterExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +52
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

Answer 1

以下代码适用于我

public class Foo
{
    public static void Main()
    {
        var myPage = "test string";
        var repo =  new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(myPage));
    }
}

似乎正确的方法是MemoryStream使用默认构造函数创建

var repo = new System.IO.MemoryStream();

然后写信给它

var stringBytes = System.Text.Encoding.UTF8.GetBytes(myPage);
repo.Write(stringBytes, 0, stringBytes.Length);

如果您希望能够正常读取流(例如使用StreamReader),那么您还需要调用:

repo.Seek(0, SeekOrigin.Begin);

Answer 2

附加数据的自定义流会更合适。

最少测试。假设您希望在刷新流时写入文本，然后仅写入一次。

public class AppendTextFilter : Stream
{
    private Stream Filter { get; set; }
    private string Text { get; set; }
    private bool TextWritten { get; set; }

    public AppendTextFilter( Stream filter, string text )
    {
        this.Filter = filter;
        this.Text = text;
    }

    public override bool CanRead { get { return Filter.CanRead; } }

    public override bool CanSeek { get { return Filter.CanSeek; } }

    public override bool CanWrite { get { return Filter.CanWrite; } }

    public override void Flush()
    {
        if (!TextWritten)
        {
            var bytes = Encoding.UTF7.GetBytes( Text );
            Filter.Write( bytes, 0, bytes.Length );
            TextWritten = true;
        }
        Filter.Flush();
    }

    public override long Length { get { return Filter.Length + Text.Length; } }

    public override long Position
    {
        get
        {
            return Filter.Position;
        }
        set
        {
            Filter.Position = value;
        }
    }

    public override int Read( byte[] buffer, int offset, int count )
    {
        return Filter.Read( buffer, offset, count );
    }

    public override long Seek( long offset, SeekOrigin origin )
    {
        return Filter.Seek( offset, origin );
    }

    public override void SetLength( long value )
    {
        Filter.SetLength( value );
    }

    public override void Write( byte[] buffer, int offset, int count )
    {
        Filter.Write( buffer, offset, count );
    }
}