你可以使用

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

然后手动删除扩展:

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

    /// <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;
    }

这个实现应该可以工作。

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

字符串。LastIndexOf可以工作。

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

如果你想创建没有扩展的完整路径，你可以这样做:

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

但我想找一种更简单的方法。有人知道吗?

ReadOnlySpan<char> filename = "abc.def.ghi.txt";
var fileNameWithoutExtension = RemoveFileExtension(filename); //abc.def.ghi

string RemoveFileExtension(ReadOnlySpan<char> path)
{
    var lastPeriod = path.LastIndexOf('.');
    return (lastPeriod < 0 ? path : path[..lastPeriod]).ToString();
}