[c#] Remove file extension from a file name string

If I have a string saying "abc.txt", is there a quick way to get a substring that is just "abc"?

I can't do an fileName.IndexOf('.') because the file name could be "abc.123.txt" or something and I obviously just want to get rid of the extension (i.e. "abc.123").

    /// <summary>
    /// Get the extension from the given filename
    /// </summary>
    /// <param name="fileName">the given filename ie:abc.123.txt</param>
    /// <returns>the extension ie:txt</returns>
    public static string GetFileExtension(this string fileName)
    {
        string ext = string.Empty;
        int fileExtPos = fileName.LastIndexOf(".", StringComparison.Ordinal);
        if (fileExtPos >= 0)
            ext = fileName.Substring(fileExtPos, fileName.Length - fileExtPos);

        return ext;
    }

If you want to create full path without extension you can do something like this:

Path.Combine( Path.GetDirectoryName(fullPath), Path.GetFileNameWithoutExtension(fullPath))

but I'm looking for simpler way to do that. Does anyone have any idea?

if you want to use String operation then you can use the function lastIndexOf( ) which Searches for the last occurrence of a character or substring. Java has numerous string functions.

You can use

string extension = System.IO.Path.GetExtension(filename);

And then remove the extension manually:

string result = filename.Substring(0, filename.Length - extension.Length);

I used the below, less code

string fileName = "C:\file.docx";
MessageBox.Show(Path.Combine(Path.GetDirectoryName(fileName),Path.GetFileNameWithoutExtension(fileName)));

Output will be

C:\file

There's a method in the framework for this purpose, which will keep the full path except for the extension.

System.IO.Path.ChangeExtension(path, null);

If only file name is needed, use

System.IO.Path.GetFileNameWithoutExtension(path);

String.LastIndexOf would work.

string fileName= "abc.123.txt";
int fileExtPos = fileName.LastIndexOf(".");
if (fileExtPos >= 0 )
 fileName= fileName.Substring(0, fileExtPos);

This implementation should work.

string file = "abc.txt";
string fileNoExtension = file.Replace(".txt", "");

        private void btnfilebrowse_Click(object sender, EventArgs e)
        {
            OpenFileDialog dlg = new OpenFileDialog();
            //dlg.ShowDialog();
            dlg.Filter = "CSV files (*.csv)|*.csv|XML files (*.xml)|*.xml";
            if (dlg.ShowDialog() == DialogResult.OK)
            {
                string fileName;
                fileName = dlg.FileName;
                string filecopy;
                filecopy = dlg.FileName;
                filecopy = Path.GetFileName(filecopy);
                string strFilename;
                strFilename = filecopy;
                 strFilename = strFilename.Substring(0, strFilename.LastIndexOf('.'));
                //fileName = Path.GetFileName(fileName);             

                txtfilepath.Text = strFilename;

                string filedest = System.IO.Path.GetFullPath(".\\Excels_Read\\'"+txtfilepath.Text+"'.csv");
               // filedest = "C:\\Users\\adm\\Documents\\Visual Studio 2010\\Projects\\ConvertFile\\ConvertFile\\Excels_Read";
                FileInfo file = new FileInfo(fileName);
                file.CopyTo(filedest);
             // File.Copy(fileName, filedest,true);
                MessageBox.Show("Import Done!!!");
            }
        }

You maybe not asking the UWP api. But in UWP, file.DisplayName is the name without extensions. Hope useful for others.

I know it's an old question and Path.GetFileNameWithoutExtensionis a better and maybe cleaner option. But personally I've added this two methods to my project and wanted to share them. This requires C# 8.0 due to it using ranges and indices.

public static string RemoveExtension(this string file) => ReplaceExtension(file, null);

public static string ReplaceExtension(this string file, string extension)
{
    var split = file.Split('.');

    if (string.IsNullOrEmpty(extension))
        return string.Join(".", split[..^1]);

    split[^1] = extension;

    return string.Join(".", split);
}