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Directory::EnumerateFileSystemEntries Method (String, String, SearchOption)

Returns an enumerable collection of file names and directory names that match a search pattern in a specified path, and optionally searches subdirectories.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)

public:
static IEnumerable<String^>^ EnumerateFileSystemEntries(
	String^ path, 
	String^ searchPattern, 
	SearchOption searchOption
)

Parameters

path
Type: System::String

The relative or absolute path to the directory to search. This string is not case-sensitive.

searchPattern
Type: System::String

The search string to match against file-system entries in path. This parameter can contain a combination of valid literal path and wildcard (* and ?) characters (see Remarks), but doesn't support regular expressions.

searchOption
Type: System.IO::SearchOption

One of the enumeration values that specifies whether the search operation should include only the current directory or should include all subdirectories.

The default value is TopDirectoryOnly.

Return Value

Type: System.Collections.Generic::IEnumerable<String>
An enumerable collection of file-system entries in the directory specified by path and that match the specified search pattern and option.

ExceptionCondition
ArgumentException

path is a zero-length string, contains only white space, or contains invalid characters. You can query for invalid characters by using the GetInvalidPathChars method.

- or -

searchPattern does not contain a valid pattern.

ArgumentNullException

path is nullptr.

-or-

searchPattern is nullptr.

ArgumentOutOfRangeException

searchOption is not a valid SearchOption value.

DirectoryNotFoundException

path is invalid, such as referring to an unmapped drive.

IOException

path is a file name.

PathTooLongException

The specified path, file name, or combined exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters and file names must be less than 260 characters.

SecurityException

The caller does not have the required permission.

UnauthorizedAccessException

The caller does not have the required permission.

searchPattern can be a combination of literal and wildcard characters, but doesn't support regular expressions. The following wildcard specifiers are permitted in searchPattern.

Wildcard specifier

Matches

* (asterisk)

Zero or more characters in that position.

? (question mark)

Zero or one character in that position.

Characters other than the wildcard are literal characters. For example, the searchPattern string "*t" searches for all names in path ending with the letter "t". The searchPattern string "s*" searches for all names in path beginning with the letter "s".

NoteNote

When you use the asterisk wildcard character in a searchPattern such as "*.txt", the number of characters in the specified extension affects the search as follows:

  • If the specified extension is exactly three characters long, the method returns files with extensions that begin with the specified extension. For example, "*.xls" returns both "book.xls" and "book.xlsx".

  • In all other cases, the method returns files that exactly match the specified extension. For example, "*.ai" returns "file.ai" but not "file.aif".

When you use the question mark wildcard character, this method returns only files that match the specified file extension. For example, given two files, "file1.txt" and "file1.txtother", in a directory, a search pattern of "file?.txt" returns just the first file, whereas a search pattern of "file*.txt" returns both files.

searchPattern cannot end in two periods ("..") or contain two periods ("..") followed by DirectorySeparatorChar or AltDirectorySeparatorChar, nor can it contain any invalid characters. You can query for invalid characters by using the GetInvalidPathChars method.

You can specify relative path information with the path parameter. Relative path information is interpreted as relative to the current working directory, which you can determine by using the GetCurrentDirectory method.

The EnumerateFileSystemEntries and GetFileSystemEntries methods differ as follows: When you use EnumerateFileSystemEntries, you can start enumerating the collection of entries before the whole collection is returned; when you use GetFileSystemEntries, you must wait for the whole array of entries to be returned before you can access the array. Therefore, when you are working with many files and directories, EnumerateFiles can be more efficient.

The returned collection is not cached; each call to the GetEnumerator on the collection will start a new enumeration.

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4
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