I want to use Linq to query a 2D array but I get an error:
Could not find an implementation of the query pattern for source type 'SimpleGame.ILandscape[,]'. 'Select' not found. Are you missing a reference to 'System.Core.dll' or a using directive for 'System.Linq'?
Code is following:
var doors = from landscape in this.map select landscape;
I've checked that I included the reference System.Core and using System.Linq.
Could anyone give some possible causes?
In order to use your multidimensional array with LINQ, you simply need to convert it to IEnumerable<T>. It's simple enough, here are two example options for querying
int[,] array = { { 1, 2 }, { 3, 4 } };
var query = from int item in array
where item % 2 == 0
select item;
var query2 = from item in array.Cast<int>()
where item % 2 == 0
select item;
Each syntax will convert the 2D array into an IEnumerable<T> (because you say int item in one from clause or array.Cast<int>() in the other). You can then filter, select, or perform whatever projection you wish using LINQ methods.
IEnumerable<T> is not required for the foreach looping structure. Array implements IEnumerable, and this fits the requirement. For the foreach, the structure needs to implement/be implicitly convertible to an enumerable interface (IEnumerable or IEnumerable<T>) or have appropriate GetEnumerator and MoveNext methods. See section 8.8.4 of the C# language specification for more details.Your map is a multidimensional array--these do not support LINQ query operations (see more Why do C# Multidimensional arrays not implement IEnumerable<T>?)
You'll need to either flatten the storage for your array (probably the best way to go for many reasons) or write some custom enumeration code for it:
public IEnumerable<T> Flatten<T>(T[,] map) {
for (int row = 0; row < map.GetLength(0); row++) {
for (int col = 0; col < map.GetLength(1); col++) {
yield return map[row,col];
}
}
}
