将过滤器设置为OpenFileDialog以允许典型的图像格式？

我有这段代码，如何允许它接受所有典型的图像格式？PNG，JPEG，JPG，GIF？

这是我到目前为止的内容：

public void EncryptFile()
{            
    OpenFileDialog dialog = new OpenFileDialog();
    dialog.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*";
    dialog.InitialDirectory = @"C:\";
    dialog.Title = "Please select an image file to encrypt.";

    if (dialog.ShowDialog() == DialogResult.OK)
    {
        //Encrypt the selected file. I'll do this later. :)
    }             
}

请注意，筛选器设置为.txt文件。我可以更改为PNG，但是其他类型是什么？

从该文档中，过滤器语法，您需要的是如下：

Office Files|*.doc;*.xls;*.ppt

也就是说，用分号分隔多个扩展名-因此，Image Files|*.jpg;*.jpeg;*.png;...。

如果浏览图像文件，请遵循以下模式：

dialog.Filter =  "Image files (*.jpg, *.jpeg, *.jpe, *.jfif, *.png) | *.jpg; *.jpeg; *.jpe; *.jfif; *.png";

这是ImageCodecInfo建议的示例（在VB中）：

   Imports System.Drawing.Imaging
        ...            

        Dim ofd as new OpenFileDialog()
        ofd.Filter = ""
        Dim codecs As ImageCodecInfo() = ImageCodecInfo.GetImageEncoders()
        Dim sep As String = String.Empty
        For Each c As ImageCodecInfo In codecs
            Dim codecName As String = c.CodecName.Substring(8).Replace("Codec", "Files").Trim()
            ofd.Filter = String.Format("{0}{1}{2} ({3})|{3}", ofd.Filter, sep, codecName, c.FilenameExtension)
            sep = "|"
        Next
        ofd.Filter = String.Format("{0}{1}{2} ({3})|{3}", ofd.Filter, sep, "All Files", "*.*")

它看起来像这样：

C＃的完整解决方案在这里：

private void btnSelectImage_Click(object sender, RoutedEventArgs e)
{
    // Configure open file dialog box 
    Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
    dlg.Filter = "";

    ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
    string sep = string.Empty;

    foreach (var c in codecs)
    {
       string codecName = c.CodecName.Substring(8).Replace("Codec", "Files").Trim();
       dlg.Filter = String.Format("{0}{1}{2} ({3})|{3}", dlg.Filter, sep, codecName, c.FilenameExtension);
       sep = "|";
    }

    dlg.Filter = String.Format("{0}{1}{2} ({3})|{3}", dlg.Filter, sep, "All Files", "*.*"); 

    dlg.DefaultExt = ".png"; // Default file extension 

    // Show open file dialog box 
    Nullable<bool> result = dlg.ShowDialog();

    // Process open file dialog box results 
    if (result == true)
    {
       // Open document 
       string fileName  = dlg.FileName;
       // Do something with fileName  
    }
} 

要过滤图像文件，请使用此代码示例。

//Create a new instance of openFileDialog
OpenFileDialog res = new OpenFileDialog();

//Filter
res.Filter = "Image Files|*.jpg;*.jpeg;*.png;*.gif;*.tif;...";

//When the user select the file
if (res.ShowDialog() == DialogResult.OK)
{
   //Get the file's path
   var filePath = res.FileName;
   //Do something
   ....
}

我最喜欢汤姆·浮士德的答案。这是他的解决方案的C＃版本，但简化了一点。

var codecs = ImageCodecInfo.GetImageEncoders(); 
var codecFilter = "Image Files|"; 
foreach (var codec in codecs) 
{
    codecFilter += codec.FilenameExtension + ";"; 
} 
dialog.Filter = codecFilter;

对于图像，您可以从GDI（System.Drawing）获取可用的编解码器，并通过一些工作就可以从中构建列表。这将是最灵活的方法。

ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();

只是使用string.Join和LINQ的一个小技巧。

ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
dlgOpenMockImage.Filter = string.Format("{0}| All image files ({1})|{1}|All files|*", 
    string.Join("|", codecs.Select(codec => 
    string.Format("{0} ({1})|{1}", codec.CodecName, codec.FilenameExtension)).ToArray()),
    string.Join(";", codecs.Select(codec => codec.FilenameExtension).ToArray()));

对于那些不想每次都记住语法的人，这里有一个简单的封装：

public class FileDialogFilter : List<string>
{
    public string Explanation { get; }

    public FileDialogFilter(string explanation, params string[] extensions)
    {
        Explanation = explanation;
        AddRange(extensions);
    }

    public string GetFileDialogRepresentation()
    {
        if (!this.Any())
        {
            throw new ArgumentException("No file extension is defined.");
        }

        StringBuilder builder = new StringBuilder();

        builder.Append(Explanation);

        builder.Append(" (");
        builder.Append(String.Join(", ", this));
        builder.Append(")");

        builder.Append("|");
        builder.Append(String.Join(";", this));

        return builder.ToString();
    }
}

public class FileDialogFilterCollection : List<FileDialogFilter>
{
    public string GetFileDialogRepresentation()
    {
        return String.Join("|", this.Select(filter => filter.GetFileDialogRepresentation()));
    }
}

用法：

FileDialogFilter filterImage = new FileDialogFilter("Image Files", "*.jpeg", "*.bmp");
FileDialogFilter filterOffice = new FileDialogFilter("Office Files", "*.doc", "*.xls", "*.ppt");

FileDialogFilterCollection filters = new FileDialogFilterCollection
{
    filterImage,
    filterOffice
};

OpenFileDialog fileDialog = new OpenFileDialog
{
    Filter = filters.GetFileDialogRepresentation()
};

fileDialog.ShowDialog();

为了匹配文件的不同类别的列表，可以使用如下过滤器：

        var dlg = new Microsoft.Win32.OpenFileDialog()
        {
            DefaultExt = ".xlsx",
            Filter = "Excel Files (*.xls, *.xlsx)|*.xls;*.xlsx|CSV Files (*.csv)|*.csv"
        };

这是极端的情况，但是我使用名为FILE_TYPES的两列数据库表构建了一个动态的数据库驱动的过滤器，其字段名称为EXTENSION和DOCTYPE：

---------------------------------
| EXTENSION  |  DOCTYPE         |
---------------------------------
|   .doc     |  Document        |
|   .docx    |  Document        |
|   .pdf     |  Document        |
|   ...      |  ...             |
|   .bmp     |  Image           |
|   .jpg     |  Image           |
|   ...      |  ...             |
---------------------------------

显然，我有许多不同的类型和扩展名，但在此示例中我将其简化。这是我的功能：

    private static string GetUploadFilter()
    {
        // Desired format:
        // "Document files (*.doc, *.docx, *.pdf)|*.doc;*.docx;*.pdf|"
        // "Image files (*.bmp, *.jpg)|*.bmp;*.jpg|"

        string filter = String.Empty;
        string nameFilter = String.Empty;
        string extFilter = String.Empty;

        // Used to get extensions
        DataTable dt = new DataTable();
        dt = DataLayer.Get_DataTable("SELECT * FROM FILE_TYPES ORDER BY EXTENSION");

        // Used to cycle through doctype groupings ("Images", "Documents", etc.)
        DataTable dtDocTypes = new DataTable();
        dtDocTypes = DataLayer.Get_DataTable("SELECT DISTINCT DOCTYPE FROM FILE_TYPES ORDER BY DOCTYPE");

        // For each doctype grouping...
        foreach (DataRow drDocType in dtDocTypes.Rows)
        {
            nameFilter = drDocType["DOCTYPE"].ToString() + " files (";

            // ... add its associated extensions
            foreach (DataRow dr in dt.Rows)
            {
                if (dr["DOCTYPE"].ToString() == drDocType["DOCTYPE"].ToString())
                {
                    nameFilter += "*" + dr["EXTENSION"].ToString() + ", ";
                    extFilter += "*" + dr["EXTENSION"].ToString() + ";";
                }                    
            }

            // Remove endings put in place in case there was another to add, and end them with pipe characters:
            nameFilter = nameFilter.TrimEnd(' ').TrimEnd(',');
            nameFilter += ")|";
            extFilter = extFilter.TrimEnd(';');
            extFilter += "|";

            // Add the name and its extensions to our main filter
            filter += nameFilter + extFilter;

            extFilter = ""; // clear it for next round; nameFilter will be reset to the next DOCTYPE on next pass
        }

        filter = filter.TrimEnd('|');
        return filter;
    }

    private void UploadFile(string fileType, object sender)
    {            
        Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
        string filter = GetUploadFilter();
        dlg.Filter = filter;

        if (dlg.ShowDialog().Value == true)
        {
            string fileName = dlg.FileName;

            System.IO.FileStream fs = System.IO.File.OpenRead(fileName);
            byte[] array = new byte[fs.Length];

            // This will give you just the filename
            fileName = fileName.Split('\\')[fileName.Split('\\').Length - 1];
            ...

应该产生一个看起来像这样的过滤器：