如何创建文件或文件夹（C# 编程指南）

  • 项目

可通过编程方式在计算机上创建文件夹、子文件夹和子文件夹中的文件，并将数据写入文件。

示例

public class CreateFileOrFolder
{
    static void Main()
    {
        // Specify a name for your top-level folder.
        string folderName = @"c:\Top-Level Folder";

        // To create a string that specifies the path to a subfolder under your
        // top-level folder, add a name for the subfolder to folderName.
        string pathString = System.IO.Path.Combine(folderName, "SubFolder");

        // You can write out the path name directly instead of using the Combine
        // method. Combine just makes the process easier.
        string pathString2 = @"c:\Top-Level Folder\SubFolder2";

        // You can extend the depth of your path if you want to.
        //pathString = System.IO.Path.Combine(pathString, "SubSubFolder");

        // Create the subfolder. You can verify in File Explorer that you have this
        // structure in the C: drive.
        //    Local Disk (C:)
        //        Top-Level Folder
        //            SubFolder
        System.IO.Directory.CreateDirectory(pathString);

        // Create a file name for the file you want to create.
        string fileName = System.IO.Path.GetRandomFileName();

        // This example uses a random string for the name, but you also can specify
        // a particular name.
        //string fileName = "MyNewFile.txt";

        // Use Combine again to add the file name to the path.
        pathString = System.IO.Path.Combine(pathString, fileName);

        // Verify the path that you have constructed.
        Console.WriteLine("Path to my file: {0}\n", pathString);

        // Check that the file doesn't already exist. If it doesn't exist, create
        // the file and write integers 0 - 99 to it.
        // DANGER: System.IO.File.Create will overwrite the file if it already exists.
        // This could happen even with random file names, although it is unlikely.
        if (!System.IO.File.Exists(pathString))
        {
            using (System.IO.FileStream fs = System.IO.File.Create(pathString))
            {
                for (byte i = 0; i < 100; i++)
                {
                    fs.WriteByte(i);
                }
            }
        }
        else
        {
            Console.WriteLine("File \"{0}\" already exists.", fileName);
            return;
        }

        // Read and display the data from your file.
        try
        {
            byte[] readBuffer = System.IO.File.ReadAllBytes(pathString);
            foreach (byte b in readBuffer)
            {
                Console.Write(b + " ");
            }
            Console.WriteLine();
        }
        catch (System.IO.IOException e)
        {
            Console.WriteLine(e.Message);
        }

        // Keep the console window open in debug mode.
        System.Console.WriteLine("Press any key to exit.");
        System.Console.ReadKey();
    }
    // Sample output:

    // Path to my file: c:\Top-Level Folder\SubFolder\ttxvauxe.vv0

    //0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
    //30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56
    // 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 8
    //3 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
}

如果文件夹已存在，CreateDirectory 不执行任何操作，未引发任何异常。 但 File.Create 用新文件替换现有文件。 本示例使用 if-else 语句阻止替换现有文件。

通过在示例中作出以下更改，可根据具有特定名称的文件是否存在来指定不同的结果。 如果该文件不存在，代码就会创建一个文件。 如果该文件存在，代码就会将数据追加到该文件中。

  • 指定一个非随机文件名。

    // Comment out the following line.  
//string fileName = System.IO.Path.GetRandomFileName();  

// Replace that line with the following assignment.  
string fileName = "MyNewFile.txt";

  • 用以下代码中的 using 语句替换 if-else 语句。

    using (System.IO.FileStream fs = new System.IO.FileStream(pathString, FileMode.Append))
{  
    for (byte i = 0; i < 100; i++)  
    {  
        fs.WriteByte(i);  
    }  
}

多次运行此示例，验证数据是否每次都添加到了文件中。

有关可尝试的 FileMode 值，请参阅 FileMode。

以下情况可能会导致异常：

.NET 安全性

可能在部分信任场景中引发 SecurityException 类的实例。

如果没有创建文件夹的权限，则本示例引发 UnauthorizedAccessException 类的实例。

请参阅