apewer-dotnet/Apewer/Source/TableIndex.cs

using System;

namespace Apewer.Source
{

    /// <summary>索引。</summary>
    public sealed class TableIndex
    {

        /// <summary>索引名称。</summary>
        public string Name { get; }

        /// <summary>表。</summary>
        public TableAttribute Table { get; }

        /// <summary>索引字段。</summary>
        public IndexAttribute[] Fields { get; }

        /// <summary>创建索引实例。</summary>
        /// <exception cref="ArgumentNullException"></exception>
        internal TableIndex(string name, TableAttribute table, IndexAttribute[] fields)
        {
            if (name.IsEmpty()) throw new ArgumentNullException(nameof(name));
            if (table == null) throw new ArgumentNullException(nameof(table));
            if (fields == null) throw new ArgumentNullException(nameof(fields));

            Name = name;
            Table = table;
            Fields = fields;
        }

        /// <summary></summary>
        public override string ToString()
        {
            var fields = Fields.FindAll(x => x != null && x.Column != null);
            if (fields.IsEmpty()) return Name;

            var array = fields.Map(x => x.Order == Order.Ascend ? x.Column.Field : $"{x.Column.Field} DESC");
            return $"{Name} ({array.Join(", ")})";
        }

    }

}