Question

This is probably pretty subjective, but how do people generally lay out their loop control in C# when the control variable is updated in the loop? The pedant in me doesn’t like the separate declaration and repetition involved. eg.

string line = reader.ReadLine();
while (line != null)
{
    //do something with line

    line = reader.ReadLine();
}

The C coder in me wants to change this to

while (string line = reader.ReadLine() != null)
{
    //do something with line
}

but C#’s expressions don’t seem to work that way 🙁

Answer 1

You can’t declare a variable inside an expression.

You can write

string line;
while (line = reader.ReadLine() != null)

To make it clearer, I prefer to write

string line;
while (null != (line = reader.ReadLine()))

However, the best alternative is

foreach(string line in File.ReadLines(path) {

}

This will perform equivalently.
If you’re reading some other stream, you can create an extension method that uses the previous syntax to enable foreach loops.