有很多軟件如"WinRar" 能在它的文件列表中顯示各類文件相關的圖標。

在網上查了一下，發現可以用 SHGetFileInfo、ExtractAssociatedIcon等winapi函數根據文件獲取文件在系統中對應的圖標。

剛開始用的時候覺得好像它們只能返回存在的文件的圖標。 若要用這些函數去根據擴展名獲取圖標，則需要先創建一個假文件, 獲取圖標后又刪除，太麻煩。

后來重新查了一下，發現用SHGetFileInfo函數可以根據擴展名獲取文件圖標。

以下為示例代碼。

using?System;
using?System.Drawing;
using?System.Collections;
using?System.ComponentModel;
using?System.Data;
using?System.Runtime.InteropServices;

namespace?IconHelper
{
????/**////?<summary>
????///?Provides?static?methods?to?read?system?icons?for?both?folders?and?files.
????///?</summary>
????///?<example>
????///?<code>IconReader.GetFileIcon("c:\\general.xls");</code>
????///?</example>
????public?class?IconReader
????{
????????/**////?<summary>
????????///?Options?to?specify?the?size?of?icons?to?return.
????????///?</summary>
????????public?enum?IconSize
????????{
????????????/**////?<summary>
????????????///?Specify?large?icon?-?32?pixels?by?32?pixels.
????????????///?</summary>
????????????Large?=?0,
????????????/**////?<summary>
????????????///?Specify?small?icon?-?16?pixels?by?16?pixels.
????????????///?</summary>
????????????Small?=?1
????????}

????????/**////?<summary>
????????///?Options?to?specify?whether?folders?should?be?in?the?open?or?closed?state.
????????///?</summary>
????????public?enum?FolderType
????????{
????????????/**////?<summary>
????????????///?Specify?open?folder.
????????????///?</summary>
????????????Open?=?0,
????????????/**////?<summary>
????????????///?Specify?closed?folder.
????????????///?</summary>
????????????Closed?=?1
????????}

????????/**////?<summary>
????????///?Returns?an?icon?for?a?given?file?-?indicated?by?the?name?parameter.
????????///?</summary>
????????///?<param?name="name">Pathname?for?file.</param>
????????///?<param?name="size">Large?or?small</param>
????????///?<param?name="linkOverlay">Whether?to?include?the?link?icon</param>
????????///?<returns>System.Drawing.Icon</returns>
????????public?static?System.Drawing.Icon?GetFileIcon(string?name,?IconSize?size,?bool?linkOverlay)
????????{
????????????Shell32.SHFILEINFO?shfi?=?new?Shell32.SHFILEINFO();
????????????uint?flags?=?Shell32.SHGFI_ICON?|?Shell32.SHGFI_USEFILEATTRIBUTES;

????????????if?(true?==?linkOverlay)?flags?+=?Shell32.SHGFI_LINKOVERLAY;

????????????/**//*?Check?the?size?specified?for?return.?*/
????????????if?(IconSize.Small?==?size)
????????????{
????????????????flags?+=?Shell32.SHGFI_SMALLICON;
????????????}
????????????else
????????????{
????????????????flags?+=?Shell32.SHGFI_LARGEICON;
????????????}

????????????Shell32.SHGetFileInfo(name,
????????????????Shell32.FILE_ATTRIBUTE_NORMAL,
????????????????ref?shfi,
????????????????(uint)System.Runtime.InteropServices.Marshal.SizeOf(shfi),
????????????????flags);

????????????//?Copy?(clone)?the?returned?icon?to?a?new?object,?thus?allowing?us?to?clean-up?properly
????????????System.Drawing.Icon?icon?=?(System.Drawing.Icon)System.Drawing.Icon.FromHandle(shfi.hIcon).Clone();
????????????User32.DestroyIcon(shfi.hIcon);????????//?Cleanup
????????????return?icon;
????????}

????????/**////?<summary>
????????///?Used?to?access?system?folder?icons.
????????///?</summary>
????????///?<param?name="size">Specify?large?or?small?icons.</param>
????????///?<param?name="folderType">Specify?open?or?closed?FolderType.</param>
????????///?<returns>System.Drawing.Icon</returns>
????????public?static?System.Drawing.Icon?GetFolderIcon(IconSize?size,?FolderType?folderType)
????????{
????????????//?Need?to?add?size?check,?although?errors?generated?at?present!
????????????uint?flags?=?Shell32.SHGFI_ICON?|?Shell32.SHGFI_USEFILEATTRIBUTES;

????????????if?(FolderType.Open?==?folderType)
????????????{
????????????????flags?+=?Shell32.SHGFI_OPENICON;
????????????}

????????????if?(IconSize.Small?==?size)
????????????{
????????????????flags?+=?Shell32.SHGFI_SMALLICON;
????????????}
????????????else
????????????{
????????????????flags?+=?Shell32.SHGFI_LARGEICON;
????????????}

????????????//?Get?the?folder?icon
????????????Shell32.SHFILEINFO?shfi?=?new?Shell32.SHFILEINFO();
????????????Shell32.SHGetFileInfo(null,
????????????????Shell32.FILE_ATTRIBUTE_DIRECTORY,
????????????????ref?shfi,
????????????????(uint)System.Runtime.InteropServices.Marshal.SizeOf(shfi),
????????????????flags);

????????????System.Drawing.Icon.FromHandle(shfi.hIcon);????//?Load?the?icon?from?an?HICON?handle

????????????//?Now?clone?the?icon,?so?that?it?can?be?successfully?stored?in?an?ImageList
????????????System.Drawing.Icon?icon?=?(System.Drawing.Icon)System.Drawing.Icon.FromHandle(shfi.hIcon).Clone();

????????????User32.DestroyIcon(shfi.hIcon);????????//?Cleanup
????????????return?icon;
????????}
????}

????/**////?<summary>
????///?Wraps?necessary?Shell32.dll?structures?and?functions?required?to?retrieve?Icon?Handles?using?SHGetFileInfo.?Code
????///?courtesy?of?MSDN?Cold?Rooster?Consulting?case?study.
????///?</summary>
????///?

????//?This?code?has?been?left?largely?untouched?from?that?in?the?CRC?example.?The?main?changes?have?been?moving
????//?the?icon?reading?code?over?to?the?IconReader?type.
????public?class?Shell32
????{

????????public?const?int?MAX_PATH?=?256;
????????[StructLayout(LayoutKind.Sequential)]
????????public?struct?SHITEMID
????????{
????????????public?ushort?cb;
????????????[MarshalAs(UnmanagedType.LPArray)]
????????????public?byte[]?abID;
????????}

????????[StructLayout(LayoutKind.Sequential)]
????????public?struct?ITEMIDLIST
????????{
????????????public?SHITEMID?mkid;
????????}

????????[StructLayout(LayoutKind.Sequential)]
????????public?struct?BROWSEINFO
????????{
????????????public?IntPtr?hwndOwner;
????????????public?IntPtr?pidlRoot;
????????????public?IntPtr?pszDisplayName;
????????????[MarshalAs(UnmanagedType.LPTStr)]
????????????public?string?lpszTitle;
????????????public?uint?ulFlags;
????????????public?IntPtr?lpfn;
????????????public?int?lParam;
????????????public?IntPtr?iImage;
????????}

????????//?Browsing?for?directory.
????????public?const?uint?BIF_RETURNONLYFSDIRS?=?0x0001;
????????public?const?uint?BIF_DONTGOBELOWDOMAIN?=?0x0002;
????????public?const?uint?BIF_STATUSTEXT?=?0x0004;
????????public?const?uint?BIF_RETURNFSANCESTORS?=?0x0008;
????????public?const?uint?BIF_EDITBOX?=?0x0010;
????????public?const?uint?BIF_VALIDATE?=?0x0020;
????????public?const?uint?BIF_NEWDIALOGSTYLE?=?0x0040;
????????public?const?uint?BIF_USENEWUI?=?(BIF_NEWDIALOGSTYLE?|?BIF_EDITBOX);
????????public?const?uint?BIF_BROWSEINCLUDEURLS?=?0x0080;
????????public?const?uint?BIF_BROWSEFORCOMPUTER?=?0x1000;
????????public?const?uint?BIF_BROWSEFORPRINTER?=?0x2000;
????????public?const?uint?BIF_BROWSEINCLUDEFILES?=?0x4000;
????????public?const?uint?BIF_SHAREABLE?=?0x8000;

????????[StructLayout(LayoutKind.Sequential)]
????????public?struct?SHFILEINFO
????????{
????????????public?const?int?NAMESIZE?=?80;
????????????public?IntPtr?hIcon;
????????????public?int?iIcon;
????????????public?uint?dwAttributes;
????????????[MarshalAs(UnmanagedType.ByValTStr,?SizeConst?=?MAX_PATH)]
????????????public?string?szDisplayName;
????????????[MarshalAs(UnmanagedType.ByValTStr,?SizeConst?=?NAMESIZE)]
????????????public?string?szTypeName;
????????};

????????public?const?uint?SHGFI_ICON?=?0x000000100;?????//?get?icon
????????public?const?uint?SHGFI_DISPLAYNAME?=?0x000000200;?????//?get?display?name
????????public?const?uint?SHGFI_TYPENAME?=?0x000000400;?????//?get?type?name
????????public?const?uint?SHGFI_ATTRIBUTES?=?0x000000800;?????//?get?attributes
????????public?const?uint?SHGFI_ICONLOCATION?=?0x000001000;?????//?get?icon?location
????????public?const?uint?SHGFI_EXETYPE?=?0x000002000;?????//?return?exe?type
????????public?const?uint?SHGFI_SYSICONINDEX?=?0x000004000;?????//?get?system?icon?index
????????public?const?uint?SHGFI_LINKOVERLAY?=?0x000008000;?????//?put?a?link?overlay?on?icon
????????public?const?uint?SHGFI_SELECTED?=?0x000010000;?????//?show?icon?in?selected?state
????????public?const?uint?SHGFI_ATTR_SPECIFIED?=?0x000020000;?????//?get?only?specified?attributes
????????public?const?uint?SHGFI_LARGEICON?=?0x000000000;?????//?get?large?icon
????????public?const?uint?SHGFI_SMALLICON?=?0x000000001;?????//?get?small?icon
????????public?const?uint?SHGFI_OPENICON?=?0x000000002;?????//?get?open?icon
????????public?const?uint?SHGFI_SHELLICONSIZE?=?0x000000004;?????//?get?shell?size?icon
????????public?const?uint?SHGFI_PIDL?=?0x000000008;?????//?pszPath?is?a?pidl
????????public?const?uint?SHGFI_USEFILEATTRIBUTES?=?0x000000010;?????//?use?passed?dwFileAttribute
????????public?const?uint?SHGFI_ADDOVERLAYS?=?0x000000020;?????//?apply?the?appropriate?overlays
????????public?const?uint?SHGFI_OVERLAYINDEX?=?0x000000040;?????//?Get?the?index?of?the?overlay

????????public?const?uint?FILE_ATTRIBUTE_DIRECTORY?=?0x00000010;
????????public?const?uint?FILE_ATTRIBUTE_NORMAL?=?0x00000080;

????????[DllImport("Shell32.dll")]
????????public?static?extern?IntPtr?SHGetFileInfo(
????????????string?pszPath,
????????????uint?dwFileAttributes,
????????????ref?SHFILEINFO?psfi,
????????????uint?cbFileInfo,
????????????uint?uFlags
????????????);
????}

????/**////?<summary>
????///?Wraps?necessary?functions?imported?from?User32.dll.?Code?courtesy?of?MSDN?Cold?Rooster?Consulting?example.
????///?</summary>
????public?class?User32
????{
????????/**////?<summary>
????????///?Provides?access?to?function?required?to?delete?handle.?This?method?is?used?internally
????????///?and?is?not?required?to?be?called?separately.
????????///?</summary>
????????///?<param?name="hIcon">Pointer?to?icon?handle.</param>
????????///?<returns>N/A</returns>
????????[DllImport("User32.dll")]
????????public?static?extern?int?DestroyIcon(IntPtr?hIcon);
????}
}

轉載于:https://www.cnblogs.com/TianFang/archive/2006/05/24/407620.html

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