File.AppendAllLines Method (String, IEnumerable<String>)
Appends lines to a file, and then closes the file. If the specified file does not exist, this method creates a file, writes the specified lines to the file, and then closes the file.
Namespace: System.IO
Assembly: mscorlib (in mscorlib.dll)
Parameters
- path
- Type: System.String
The file to append the lines to. The file is created if it doesn't already exist.
- contents
- Type: System.Collections.Generic.IEnumerable<String>
The lines to append to the file.
| Exception | Condition |
|---|---|
| ArgumentException | path is a zero-length string, contains only white space, or contains one more invalid characters defined by the GetInvalidPathChars method. |
| ArgumentNullException | Either path or contents is null. |
| DirectoryNotFoundException | path is invalid (for example, the directory doesn’t exist or it is on an unmapped drive). |
| FileNotFoundException | The file specified by path was not found. |
| IOException | An I/O error occurred while opening the file. |
| PathTooLongException | path exceeds 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. |
| NotSupportedException | path is in an invalid format. |
| SecurityException | The caller does not have permission to write to the file. |
| UnauthorizedAccessException | path specifies a file that is read-only. -or- This operation is not supported on the current platform. -or- path is a directory. |
The following example writes selected lines from a sample data file to a file, and then appends more lines. The directory named temp on drive C must exist for the example to complete successfully.
using System; using System.IO; using System.Linq; class Program { static string dataPath = @"c:\temp\timestamps.txt"; static void Main(string[] args) { CreateSampleFile(); var JulyWeekends = from line in File.ReadLines(dataPath) where (line.StartsWith("Saturday") || line.StartsWith("Sunday")) & line.Contains("July") select line; File.WriteAllLines(@"C:\temp\selectedDays.txt", JulyWeekends); var MarchMondays = from line in File.ReadLines(dataPath) where line.StartsWith("Monday") && line.Contains("March") select line; File.AppendAllLines(@"C:\temp\selectedDays.txt", MarchMondays); } static void CreateSampleFile() { DateTime TimeStamp = new DateTime(1700, 1, 1); using (StreamWriter sw = new StreamWriter(dataPath)) { for (int i = 0; i < 500; i++) { DateTime TS1 = TimeStamp.AddYears(i); DateTime TS2 = TS1.AddMonths(i); DateTime TS3 = TS2.AddDays(i); sw.WriteLine(TS3.ToLongDateString()); } } } }
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
