// Instance of query class.
var selectQuery = new SelectQuery()
{
    // Root schema name.
    RootSchemaName = "Contact",
    // Adding columns to query.
    Columns = new SelectQueryColumns()
    {
        // Collection of columns.
        Items = new Dictionary<string, SelectQueryColumn>()
        {
            //Column [Full name].
            {
                // Key.
                "Name",
                // Value.
                new SelectQueryColumn()
                {
                    // Expression that specifies the column type.
                    Expression = new ColumnExpression()
                    {
                        // Type of expression - schema column.
                        ExpressionType = EntitySchemaQueryExpressionType.SchemaColumn,
                        // Pat to column.
                        ColumnPath = "Name"
                    }
                }
            },
            // Column [Number of activities].
            {
                "ActivitiesCount",
                new SelectQueryColumn()
                {
                    Expression = new ColumnExpression()
                    {
                        // Expression type — subquery.
                        ExpressionType = EntitySchemaQueryExpressionType.SubQuery,
                        // Path to column relative to the oot schema.
                        ColumnPath = "[Activity:Contact].Id",
                        // Function tyoe — aggregation.
                        FunctionType = FunctionType.Aggregation,
                        // Aggregation type — quantity.
                        AggregationType = AggregationType.Count
                    }
                }
            }
        }
    }
};

// Query filters.
var selectFilters = new Filters()
{
    // Filter type — group.
    FilterType = Terrasoft.Nui.ServiceModel.DataContract.FilterType.FilterGroup,
    // Filter collection.
    Items = new Dictionary<string, Filter>
    {
        
        // Filter by year of birth.
        {
            // Key.
            "FilterYear",
            // Value.
            new Filter
            {
                // Filter type — comparison.
                FilterType = Terrasoft.Nui.ServiceModel.DataContract.FilterType.CompareFilter,
                // Comparison type — equal.
                ComparisonType = FilterComparisonType.Equal,
                // Expression to check.
                LeftExpression = new BaseExpression()
                {
                    // Expression type — schema column.
                    ExpressionType = EntitySchemaQueryExpressionType.SchemaColumn,
                    // Path to schema.
                    ColumnPath = "BirthDate"
                },
                // Expression with which the checked value is compared.
                RightExpression = new BaseExpression
                {
                    // Expression type — function.
                    ExpressionType = EntitySchemaQueryExpressionType.Function,
                    // Function type — macro.
                    FunctionType = FunctionType.Macros,
                    // Macro type — year.
                    MacrosType = EntitySchemaQueryMacrosType.Year,
                    // Function argument.
                    FunctionArgument = new BaseExpression
                    {
                        // Type of expression that determines the argument — parameter.
                        ExpressionType = EntitySchemaQueryExpressionType.Parameter,
                        // Parameter initialization.
                        Parameter = new Parameter
                        {
                            // Parameter type — integer.
                            DataValueType = DataValueType.Integer,
                            // Parameter value.
                            Value = "1992"
                        }
                    }
                }
            }
        }
    }
};
// Adding filters to query.
selectQuery.Filters = selectFilters;
// Serialization of select query class instance in a JSON string.
var json = new JavaScriptSerializer().Serialize(selectQuery);