[c#] How do I create directory if it doesn't exist to create a file?

I have a piece of code here that breaks if the directory doesn't exist:

System.IO.File.WriteAllText(filePath, content);

In one line (or a few lines), is it possible to check if the directory leading to the new file doesn't exist and if not, to create it before creating the new file?

I'm using .NET 3.5.

You can use File.Exists to check if the file exists and create it using File.Create if required. Make sure you check if you have access to create files at that location.

Once you are certain that the file exists, you can write to it safely. Though as a precaution, you should put your code into a try...catch block and catch for the exceptions that function is likely to raise if things don't go exactly as planned.

Additional information for basic file I/O concepts.

var filePath = context.Server.MapPath(Convert.ToString(ConfigurationManager.AppSettings["ErrorLogFile"]));

var file = new FileInfo(filePath);

file.Directory.Create(); If the directory already exists, this method does nothing.

var sw = new StreamWriter(filePath, true);

sw.WriteLine(Enter your message here);

sw.Close();

As @hitec said, you have to be sure that you have the right permissions, if you do, you can use this line to ensure the existence of the directory:

Directory.CreateDirectory(Path.GetDirectoryName(filePath))

You can use following code

  DirectoryInfo di = Directory.CreateDirectory(path);

An elegant way to move your file to an nonexistent directory is to create the following extension to native FileInfo class:

public static class FileInfoExtension
{
    //second parameter is need to avoid collision with native MoveTo
    public static void MoveTo(this FileInfo file, string destination, bool autoCreateDirectory) { 

        if (autoCreateDirectory)
        {
            var destinationDirectory = new DirectoryInfo(Path.GetDirectoryName(destination));

            if (!destinationDirectory.Exists)
                destinationDirectory.Create();
        }

        file.MoveTo(destination);
    }
}

Then use brand new MoveTo extension:

 using <namespace of FileInfoExtension>;
 ...
 new FileInfo("some path")
     .MoveTo("target path",true);

Check Methods extension documentation.