. NET under the operation of MongoDB (ii)

This time, the use of C#driver, MongoDB for a simple query.

We can use the static method in the query class to create a series of queries to achieve the purpose of the query.

Query is in the using MongoDB.Driver.Builders namespace.

1. Single condition query, you can refer to the following code:

            var query = Query.eq ("ColName", "Value");            foreach (Bsondocument doc in collection. Find (query)            {                Debug.WriteLine (doc["colname"). ToString () + "\ t");            }

2. To make a combination of conditions, such as and, or or, refer to the code:

            var query = query.or (                query.eq ("ColName1", "Value1"),                query.eq ("ColName2", "Value2")                );            foreach (Bsondocument doc in Dotnetcollection.find (query))            {                Debug.WriteLine (doc["ColName1"]. ToString () + "\ T" +         doc["ColName2"]. ToString ());            }        

Using these QueryBuilder to create a query is a recommended method for MongoDB, simple and clear.

3. To return the specified object, you can refer to the code:

            var query = Query<table1>. EQ (b = b.testcol1, "BBB");            foreach (table1 ele in dotnetcollection.findas<table1> (query))            {                Debug.WriteLine (ele.testcol1 + "\ T") + ele.testcol2);            }

where table1 is defined as:

        public class table1        {public            ObjectId _id {get; set;}            public string TestCol1 {get; set;}            public string TestCol2 {get; set;}        }

It is important to note that _id must contain this attribute, ObjectId is MongoDB.Bson.ObjectId, otherwise it will produce "Element ' _id ' does not match any field or property in the data reading. Class "This error.