MongoDB C# driver 2.0: How to get the result from MapReduceAsync
I'm using MongoDB version 3, C# driver 2.0 and would get the result of MapReduceAsync method. I have this collection "users":
{ "_id" : 1, "firstName" : "Rich", "age" : "18" }
{ "_id" : 2, "firstName" : "Rob", "age" : "25" }
{ "_id" : 3, "firstName" : "Sarah", "age" : "12" }
The code in VisualStudio:
var map = new BsonJavaScript( @"
var map = function()
{
emit(NumberInt(1), this.age);
};");
var reduce = new BsonJavaScript(@"
var reduce = function(key, values)
{
var sum = 0;
values.forEach(function(item)
{
sum += NumberInt(item);
});
return sum;
};");
var coll = db.GetCollection<BsonDocument>("users");
var options = new MapReduceOptions<BsonDocument, TResult>();//what should be TResult?
options.OutputOptions = MapReduceOutputOptions.Inline;
var res = coll.MapReduceAsync(map, reduce, options).Result.ToListAsync();
//get the values of res...
//or if the result is a list...
foreach(var item in res)
{
//get the values and do something...
}
TResult can be a BsonDocument or a specific class which represent the result of type reduce item.
I think for your example, you could have a generic class like this :
public class SimpleReduceResult<T>
{
public string Id { get; set; }
public T value { get; set; }
}
And your options declaration would be
var options = new MapReduceOptions<BsonDocument, SimpleReduceResult<int>>();
来源:https://stackoverflow.com/questions/31776621/mongodb-c-sharp-driver-2-0-how-to-get-the-result-from-mapreduceasync