确定在 C# 中的 if 语句中哪个表达式不正确

Question

Let's say I have the following piece of code:

infile = new FileInfo(inputFilename);
outfile = new FileInfo(outputFilename);

if (!infile.Exists || !outfile.Exists) {
  Console.WriteLine("File missing: " + ???);
}

Is it possible to determine which of the single "if statements" was not true? ??? shall be replaced with the filename of the non-existing file.

Answer 1

Why don't you just split your if into two?

if (!infile.Exists) {
  Console.WriteLine("File missing: " + infile);
}
if (!outfile.Exists) {
  Console.WriteLine("File missing: " + outfile);
}

Answer 2

You could collect the files that do not exist and then use that collection to print the error message. For example:

var missingFiles = new FileInfo[] {inFile, outFile}.Where(f => !f.Exists);
foreach (var missingFile in missingFiles) {
    Console.WriteLine("File missing: " + missingFile);
}

Answer 3

No, not directly. However, you could write

bool infileExists = infile.Exists;
bool outfileExists = outfile.Exists;
if (!infileExists || !outfileExists) {
  Console.WriteLine("File missing: " + infileExists?"Outfile":"Infile");
}

This doesn't even need an additional evaluation of the property.