i have error sequence contains no element on below line
Microsoft.Win32.OpenFileDialog dialog = new Microsoft.Win32.OpenFileDialog();
dialog.Multiselect = true;
dialog.Filter =
loaders
.Select(loader => string.Format("{0}|{1}", loader.Metadata.Alias, loader.Metadata.ExtensionFilter))
.Aggregate((f1, f2) => f1 + "|" + f2);
dialog.Filter += "|All Files|*.*";
The overload of Enumerable.Aggregate
you're using will throw an exception if the sequence contains no elements. You can use the overload that takes a 'seed' argument: this will just return the seed if there are no elements.
loaders
.Select(loader => string.Format("{0}|{1}", loader.Metadata.Alias, loader.Metadata.ExtensionFilter))
.Aggregate(string.Empty, (f1, f2) => f1 + "|" + f2);
Better still would be to ditch aggregate altogether - you're potentially allocating lots of strings you're throwing away before you get to your result. Just use string.Join
:
var loaderFilters = loaders.Select(loader
=> string.Format("{0}|{1}", loader.Metadata.Alias, loader.Metadata.ExtensionFilter));
var allFilters = loaderFilters.Concat(new []{"All Files|*.*"});
dialog.Filter = string.Join("|", allFilters);