LINQ query and lambda expressions - linq

Question

I'm trying to write a LINQ query and am having problems. I'm not sure if lambda expressions are the answer or not but I think they may be.
I have two combo boxes on my form: "State" and "Color".
I want to select Widgets from my database based on the values of these two dropdowns.
My widgets can be in one of the following states: Not Started, In Production, In Finishing, In Inventory, Sold. Widgets can have any color in the 'color' table in the database.
The 'state' combobox has selections "Not Sold," "In Production/Finishing", "Not Started," "In Production," "In Finishing," "In Inventory," "Sold." (I hope these are self-explanatory.)
The 'color' dropdown has "All Colors," and a separate item for each color in the database.
How can I create a LINQ query to select the widgets I want from the database based on the dropdowns?

Answer 1

var WidgetStateChoosen = "Sold";
//var WidgetStateChoosen = "All Widgets";
var WidgetColourChoosen = "Orange";
//var WidgetColourChoosen = "All Colours";
var widgetselected = Widgets.Where
(w =>
( (WidgetStateChoosen == "All Widgets") ? (w.WidgetState != WidgetStateChoosen) : (w.WidgetState == WidgetStateChoosen) )
&&
( (WidgetColourChoosen == "All Colours") ? (w.WidgetColour != WidgetColourChoosen) : (w.WidgetColour == WidgetColourChoosen) )
);

Answer 2

Way more code then I wish, but oh well! I wasnt sure I completely understood your state and selectionstate, but I hope my example is still helpful.
[TestMethod]
public void SelectionTest()
{
var userSelections = GetUserSelections("AllColor", (SelectedState[])Enum.GetValues(typeof(SelectedState)));
var inventory = this.GetInventory();
foreach (var currentSelection in userSelections)
{
var selection = currentSelection;
var result = from item in inventory
where (item.Color == selection.Color || selection.Color == "AllColor") &&
this.GetStates(selection.State).Contains(item.State)
select item;
Console.WriteLine("Item selected for selection: Color:{0} SelectedState:{1}", selection.Color, selection.State);
foreach (var item in result)
{
Console.WriteLine("Item Color:{0};Item State:{1}", item.Color, item.State);
}
Console.WriteLine("");
}
}
private IEnumerable<State> GetStates(SelectedState state)
{
var list = new List<State>();
foreach (State currentState in Enum.GetValues(typeof(State)))
{
if (((int)currentState & (int)state) == (int)currentState)
{
list.Add(currentState);
}
}
return list;
}
private IEnumerable<Item> GetInventory()
{
return new List<Item>()
{
new Item() {State = State.NotStarted, Color = "Blue"},
new Item() {State = State.InFinishing, Color = "Red"},
new Item() {State = State.Sold, Color = "Yellow"},
new Item() {State = State.Sold, Color = "Blue"},
new Item() {State = State.InProduction, Color = "Blue"},
new Item() {State = State.InInventory, Color = "Blue"},
};
}
private IEnumerable<UserSelection> GetUserSelections(String color, IEnumerable<SelectedState> states)
{
var list = new List<UserSelection>();
foreach (var state in states)
{
list.Add(new UserSelection() { Color = color, State = state });
}
return list;
}
[Flags]
private enum State
{
NotStarted = 1,
InProduction = 2,
InFinishing = 4,
InInventory = 8,
Sold = 16
}
private enum SelectedState
{
NotSold = State.InInventory, //Where does it map? I assume INInventory even if it doesnt make much sense
InProductionOrFinishing = State.InProduction | State.InFinishing,
NotStarted = State.NotStarted,
InProduction = State.InProduction,
InFinishing = State.InFinishing,
InInventory = State.InInventory,
Sold = State.Sold,
SomeBizarroTrippleState = State.InProduction | State.Sold | State.NotStarted
}
private class UserSelection
{
public String Color { get; set; }
public SelectedState State { get; set; }
}
private class Item
{
public String Color { get; set; }
public State State { get; set; }
}

Answer 3

var query = db.Widgets;
if (stateFilter == "Not sold")
query = query.Where(w => w.State != WidgetState.Sold);
else if (stateFilter == "In Production/Finishing")
query = query.Where(w => w.State == WidgetState.InProduction || w.State == WidgetState.Finishing);
if (colorFilter != "All colors")
query = query.Where(w => w.Color = colorFilter);
(of course you should have a better way of testing the selected value from the combobox, testing on strings is really bad...)