Query.Select.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

namespace SqlKata
{
    public partial class Query
    {

        public Query Select(params string[] columns)
        {
            return Select(columns.AsEnumerable());
        }

        public Query Select(IEnumerable<string> columns)
        {
            Method = "select";

            columns = columns
                .Select(x => Helper.ExpandExpression(x))
                .SelectMany(x => x)
                .ToArray();


            foreach (var column in columns)
            {
                AddComponent("select", new Column
                {
                    Name = column
                });
            }

            return this;
        }

        /// <summary>
        /// Add a new "raw" select expression to the query.
        /// </summary>
        /// <returns></returns>
        public Query SelectRaw(string sql, params object[] bindings)
        {
            Method = "select";

            AddComponent("select", new RawColumn
            {
                Expression = sql,
                Bindings = bindings,
            });

            return this;
        }

        public Query Select(Query query, string alias)
        {
            Method = "select";

            query = query.Clone();

            AddComponent("select", new QueryColumn
            {
                Query = query.As(alias),
            });

            return this;
        }

        public Query Select(Func<Query, Query> callback, string alias)
        {
            return Select(callback.Invoke(NewChild()), alias);
        }

        public Query SelectAggregate(string aggregate, string column, Query filter = null)
        {
            Method = "select";

            AddComponent("select", new AggregatedColumn
            {
                Column = new Column { Name = column },
                Aggregate = aggregate,
                Filter = filter,
            });

            return this;
        }

        public Query SelectAggregate(string aggregate, string column, Func<Query, Query> filter)
        {
            if (filter == null)
            {
                return SelectAggregate(aggregate, column);
            }

            return SelectAggregate(aggregate, column, filter.Invoke(NewChild()));
        }

        public Query SelectSum(string column, Func<Query, Query> filter = null)
        {
            return SelectAggregate("sum", column, filter);
        }

        public Query SelectCount(string column, Func<Query, Query> filter = null)
        {
            return SelectAggregate("count", column, filter);
        }

        public Query SelectAvg(string column, Func<Query, Query> filter = null)
        {
            return SelectAggregate("avg", column, filter);
        }

        public Query SelectMin(string column, Func<Query, Query> filter = null)
        {
            return SelectAggregate("min", column, filter);
        }

        public Query SelectMax(string column, Func<Query, Query> filter = null)
        {
            return SelectAggregate("max", column, filter);
        }

        public Query Select<T>() where T : class {
            var properties = typeof(T).GetProperties();
            var columns = new List<string>();
            foreach (var property in properties) {
                if (property.GetSetMethod() == null) {
                    continue;
                }

                var name = property.Name;
                var attribute = property.GetCustomAttribute<ColumnAttribute>();
                if (attribute != null) {
                    name = $"{attribute.Name} as {name}";
                }

                columns.Add(name);
            }
            return Select(columns);
        }
    }
}