How do you build complex queries with MongoDB and the C# Driver?

Question

I have developed a simple API which allows you to build up an array of search criteria within a MongoDB Collection. I now need to be able to convert this array into an actual Mongo Query, and this part is where I am having extreme difficulty.

Ideally I am after some syntax that will allow me to do the following pseudo code:

var query = new QueryBuilder();
foreach (var group in groups)
{
    switch (group.Condition)
    {
        case GroupCondition.Or:
            query.Or(group.Queries);
        break;
        case GroupCondition.And:
            query.And(group.Queries);
        break;
    }
}
return myCollection.FindAs(type, query);

I actually want to build up slightly more complex queries, but ultimately I am after the functionality to dynamically build up my queries with objects as seen in my pseudo code above.

Feel free to ask me for additional details if I have not made myself clear enough about what I am trying to achieve.

Same here. I see a few people use examples of Query with multiple query expressions chained together however, when I do this like Query.EQ().GT(); it doesn't work as EQ/GT don't return a query object. What am I missing here? — Rick Strahl
– Rick Strahl, Commented Feb 27, 2014 at 19:51

Craig Wilson · Accepted Answer · 2012-08-24 01:27:10Z

4

Seems like you have the right idea... There is a class called Query that is essentially a query builder without the instantiation.

using MongoDB.Driver.Builders;

Query.And, Query.Or, etc... are all there. It is the same thing that is used underneath the linq provider to build up complex queries.

answered Aug 24, 2012 at 1:27

Craig Wilson

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3 Comments

Rick Strahl Over a year ago

Can somebody actually point at an example that shows multiple query selectors strung together? Looks like Query is not chainable.

Craig Wilson Over a year ago

@RickStrahl build it up like an AST. Query.And( Query.OR( Query.EQ("x", 1), Query.EQ("y", 2)), Query.GT("z", 3));

JustinN Over a year ago

@RickStrahl I ended up making a bespoke Query Language which breaks down, and then compiles into Mongo Queries (hence asking this question). The Query Language got scrapped in the end, but it did work (with a number of tests!). Do you still need help? I've been tempted to re-create it and public as OSS - maybe even publish a NuGet package for some of the helpers.

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