ASP.NET MVC 了解FileResult的本质

FileResult是一个基于文件的ActionResult，利用FileResult我们可以很容易地将从某个物理文件的内容响应给客户端。get='_blank'>ASP.NET MVC定义了三个具体的FileResult，分别是FileContentResult、FilePathResult和FileStreamResult。在这篇文章中我们将探讨三种具体的FileResult是如何将文件内容对请求进行响应的。

一、FileResult

如下面的代码片断所示，FileResult具有一个表示媒体类型的只读属性ContentType，该属性在构造函数中被初始化。当我们基于某个物理文件创建相应的FileResult对象的时候应该根据文件的类型指定媒体类型，比如说目标文件是一个.jpg图片，那么对应的媒体类型为“image/jpeg”，对于一个.pdf文件，则采用“application/pdf”。

public abstract class FileResult : ActionResult{  private string _fileDownloadName;      protected FileResult(string contentType)  {    if (string.IsNullOrEmpty(contentType))    {      throw new ArgumentException(MvcResources.Common_NullOrEmpty, "contentType");    }    this.ContentType = contentType;  }      public override void ExecuteResult(ControllerContext context)  {    if (context == null)    {      throw new ArgumentNullException("context");    }    HttpResponseBase response = context.HttpContext.Response;    response.ContentType = this.ContentType;    if (!string.IsNullOrEmpty(this.FileDownloadName))    {      string headerValue = ContentDispositionUtil.GetHeaderValue(this.FileDownloadName);      context.HttpContext.Response.AddHeader("Content-Disposition", headerValue);    }    this.WriteFile(response);  }      protected abstract void WriteFile(HttpResponseBase response);      public string ContentType { get; private set; }      public string FileDownloadName  {    get    {      return (this._fileDownloadName ?? string.Empty);    }    set    {      this._fileDownloadName = value;    }  }      internal static class ContentDispositionUtil  {    private const string HexDigits = "0123456789ABCDEF";          private static void AddByteToStringBuilder(byte b, StringBuilder builder)    {      builder.Append('%');      int num = b;      AddHexDigitToStringBuilder(num >> 4, builder);      AddHexDigitToStringBuilder(num % 0x10, builder);    }          private static void AddHexDigitToStringBuilder(int digit, StringBuilder builder)    {      builder.Append("0123456789ABCDEF"[digit]);    }          private static string CreateRfc2231HeaderValue(string filename)    {      StringBuilder builder = new StringBuilder("attachment; filename*=UTF-8''");      foreach (byte num in Encoding.UTF8.GetBytes(filename))      {        if (IsByteValidHeaderValueCharacter(num))        {          builder.Append((char) num);        }        else        {          AddByteToStringBuilder(num, builder);        }      }      return builder.ToString();    }          public static string GetHeaderValue(string fileName)    {      foreach (char ch in fileName)      {        if (ch > '\x007f')        {          return CreateRfc2231HeaderValue(fileName);        }      }      ContentDisposition disposition = new ContentDisposition {        FileName = fileName      };      return disposition.ToString();    }          private static bool IsByteValidHeaderValueCharacter(byte b)    {      if ((0x30 <= b) && (b <= 0x39))      {        return true;      }      if ((0x61 <= b) && (b <= 0x7a))      {        return true;      }      if ((0x41 <= b) && (b <= 90))      {        return true;      }      switch (b)      {        case 0x3a:        case 0x5f:        case 0x7e:        case 0x24:        case 0x26:        case 0x21:        case 0x2b:        case 0x2d:        case 0x2e:          return true;      }      return false;    }  }}

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原标题：ASP.NET MVC 了解FileResult的本质

关键词：ASP.NET