重构if-else语句检查不同的文件扩展名

Question

我有这段代码，我觉得可以清理（我可能是错的），但我想看看是否有人有一个建议，我可以改变这是“更好”

string getExt = Path.GetExtension(DocumentUNCPath.Text); 
     var convertFileId = Guid.NewGuid(); 
     var convertFilePath = @"c:\temp\" + convertFileId + ".pdf"; 


     if (getExt == ".doc" || getExt == ".docx" || getExt == ".txt" || getExt == ".rtf") 
     { 
      WordToPdf(convertFilePath); 

     } 
     else if (getExt == ".xlsx" || getExt == ".xls") 
     { 
      ExcelToPdf(convertFilePath); 
     } 
     else if (getExt == ".jpg" || getExt == ".png" || getExt == ".jpeg" || getExt == ".JPG" || getExt == ".PNG") 
     { 
      ImgToPDF(convertFilePath); 
     } 

Answer 1

以下可能最初是更多的代码，但可以更好地扩展。

之外的方法：

public static readonly List<string> WorkExtensions = new List<string> { ".doc", ".docx", ".txt", ".trf" }; 
    public static readonly List<string> ExcelExtensions = new List<string> { ".xlsx", ".xls" }; 
    public static readonly List<string> ImageExtensions = new List<string> { ".jpg", ".png", ".jpeg" }; 

里面的方法：

string getExt = Path.GetExtension(DocumentUNCPath.Text); 
    var convertFileId = Guid.NewGuid(); 
    var convertFilePath = @"c:\temp\" + convertFileId + ".pdf"; 

    getExt = getExt.ToLower(); 

    if (WorkExtensions.Contains(getExt)) 
    { 
     WordToPdf(convertFilePath) 
    } 
    else if (ExcelExtensions.Contains(getExt)) 
    { 
     ExcelToPdf(convertFilePath); 
    } 
    else if (ImageExtensions.Contains(getExt)) 
    { 
     ImgToPdf(convertFilePath); 
    } 

Answer 2

地图扩展处理的是这样的情况下，标准的方法：

// populate with { ".doc", WordToPdf } and similar pairs 
Dictionary<string, Action<string> > handlers = ... 


// find and call handler by extension 
// (use TryGetValue to check for existence if needed) 
handlers[getExt](convertFilePath); 

Answer 3

你可以做这样的事情

switch (getExt.ToUpper()) 
    {  
     case "JPG":  
     case "PNG": 
.... 

Answer 4

如果您正在寻找extensiblity，你可以conisder是这样的：

public struct Converter { 
    public string   Extension; 
    public Action<string> ConvertAction; 
} 

public static class Extensions { 
    static Action<string> WordToPdf = (s) => {;}; 
    static Action<string> ExcelToPdf = (s) => {;}; 
    static Action<string> ImgToPdf = (s) => {;}; 

    public static IEnumerable<Converter> Converters = new List<Converter> { 
    new Converter {Extension = ".doc", ConvertAction = WordToPdf}, 
    new Converter {Extension = ".docx", ConvertAction = WordToPdf}, 
    new Converter {Extension = ".txt", ConvertAction = WordToPdf}, 
    new Converter {Extension = ".rtf", ConvertAction = WordToPdf}, 

    new Converter {Extension = ".xls", ConvertAction = ExcelToPdf}, 
    new Converter {Extension = ".xlsx", ConvertAction = ExcelToPdf}, 

    new Converter {Extension = ".jpg", ConvertAction = ImgToPdf}, 
    new Converter {Extension = ".png", ConvertAction = ImgToPdf}, 
    new Converter {Extension = ".jpeg", ConvertAction = ImgToPdf}, 
    new Converter {Extension = ".doc", ConvertAction = ImgToPdf} 
    }; 

    public void RunIt(string extension, string convertFilePath) { 
    extension = extension.ToLower(); 
    var action = (from a in Converters 
        where a.Extension.Equals(extension) 
        select a.ConvertAction).First(); 
    if (action != null) action(convertFilePath); 
    } 
} 

Answer 5

我觉得Dictionary<string, Action<string>>以上答案是最优雅的答案，但为了完整起见，这里有一个解决方案通过串扩展：

public static class StringExt 
{ 
    public static bool MatchesAnyOf(this string text, params string[] targets) 
    { 
     return targets.Any(target => string.Compare(text, target, StringComparison.OrdinalIgnoreCase) == 0); 
    } 
} 

然后，你可以写这样的代码：

if (getExt.MatchesAnyOf(".doc", ".doxc", ".txt", ".rtf")) 
{ 
    WordToPdf(convertFilePath); 
} 
else if (getExt.MatchesAnyOf(".xlsx", ".xls")) 
{ 
    ExcelToPdf(convertFilePath); 
} 
else if (getExt.MatchesAnyOf(".jpg", ".png", ".jpeg", ".JPG", ".PNG") 
{ 
    ImgToPDF(convertFilePath); 
} 

此实现忽略大小写和文化，这是适当的文件名，但将不适合用于一般用途 - 所以真正的代码可能会提供指定文化和比较类型的重载。