Code Inspection: Co-variant array conversion
Consider the following code listing:
class MyForm : Form
{
ProcessFiles()
{
var ofd = new OpenFileDialog();
ofd.ShowDialog();
BeginInvoke(new Action<string[]>(Process), ofd.FileNames);
}
private void Process(string[] files)
{
// process each of the files
}
}
This code shows an Open File Dialog and then attempts to asynchronously process the chosen files. However, what
the developer has missed is that the
BeginInvoke()
method actually takes a params
object[]
argument, to which the developer is passing an array of strings.
As a consequence, ReSharper offers a warning, saying that the
covariant array conversion from
string[]
to
object[] may cause an exception at run-time.
The issue with the above code is easily resolved: since
BeginInvoke()
expects to receive an array of all the
parameters and there is only one parameter (string[] files),
all we have to do is provide exactly that, i.e.,
BeginInvoke(new Action<string[]>(Process), new object[]{ ofd.FileNames });