Improve performance of SqlColumnCollection; document its methods.

Author: AlexUstinov

Orm/Xtensive.Orm/Sql/Dml/Collections/SqlColumnCollection.cs

@@ -3,9 +3,8 @@
 // For conditions of distribution and use, see license.
 
 using System;
+using System.Collections;
 using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Linq;
 using Xtensive.Core;
 
 
@@ -15,74 +14,119 @@ namespace Xtensive.Sql.Dml
   /// Represents collection of <see cref="SqlColumn"/>s.
   /// </summary>
   [Serializable]
-  public class SqlColumnCollection : Collection<SqlColumn>
+  public class SqlColumnCollection : ICollection<SqlColumn>, IReadOnlyList<SqlColumn>
   {
     private static readonly StringComparer Comparer = StringComparer.OrdinalIgnoreCase;
+    private readonly List<SqlColumn> columnList;
 
-    public SqlColumn this[string name]
-    {
-      get
-      {
-        if (string.IsNullOrEmpty(name))
-          return null;
-        return this.FirstOrDefault(column => Comparer.Equals(column.Name, name));
-      }
-      set { throw new NotSupportedException(); }
-    }
+    /// <summary>
+    /// Gets the number of elements contained in the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    public int Count => columnList.Count;
 
-    public bool IsReadOnly
-    {
-      get { return false; }
-    }
+    /// <inheritdoc cref="ICollection{T}.IsReadOnly"/>>
+    bool ICollection<SqlColumn>.IsReadOnly => false;
 
-    public void Add(SqlColumn item, string alias)
-    {
-      base.Add(SqlDml.ColumnRef(item, alias));
-    }
+    /// <inheritdoc cref="IEnumerable.GetEnumerator"/>>
+    IEnumerator IEnumerable.GetEnumerator() => columnList.GetEnumerator();
 
-    public void Add(SqlExpression expression)
-    {
-      if (expression is SqlColumn)
-        base.Add(expression as SqlColumn);
-      else
-        base.Add(SqlDml.ColumnRef(SqlDml.Column(expression)));
-    }
+    /// <inheritdoc cref="IEnumerable{T}.GetEnumerator"/>>
+    IEnumerator<SqlColumn> IEnumerable<SqlColumn>.GetEnumerator() => columnList.GetEnumerator();
 
-    public void Add(SqlExpression expression, string alias)
+    /// <summary>
+    /// Returns a <see cref="List{T}.Enumerator"/> that iterates through the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    public List<SqlColumn>.Enumerator GetEnumerator() => columnList.GetEnumerator();
+
+    /// <summary>
+    /// Gets the column at the specified <paramref name="index"/>.
+    /// </summary>
+    public SqlColumn this[int index] => columnList[index];
+
+    /// <summary>
+    /// Gets the column with the specified <paramref name="name"/>
+    /// or <c>null</c> if collection doesn't contain such a column.
+    /// </summary>
+    public SqlColumn this[string name] =>
+      string.IsNullOrEmpty(name) ? null : columnList.Find(column => Comparer.Equals(column.Name, name));
+
+    /// <summary>
+    /// Adds a specified <paramref name="column"/> to the end of the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    public void Add(SqlColumn column) => columnList.Add(column);
+
+    /// <summary>
+    /// Builds a <see cref="SqlColumnRef"/> to the specified <paramref name="column"/> using
+    /// the provided <paramref name="alias"/> and then adds it to the end of the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    /// <exception cref="ArgumentNullException"><paramref name="alias"/> is null.</exception>
+    public void Add(SqlColumn column, string alias)
     {
-      ArgumentValidator.EnsureArgumentNotNull(alias, "alias");
-      base.Add(SqlDml.ColumnRef(SqlDml.Column(expression), alias));
+      ArgumentValidator.EnsureArgumentNotNull(alias, nameof(alias));
+      columnList.Add(SqlDml.ColumnRef(column, alias));
     }
 
-    public void Add(SqlColumnRef columnReference)
+    /// <summary>
+    /// Builds a <see cref="SqlColumnRef"/> by the specified <paramref name="expression"/> and
+    /// then adds it to the end of the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    public void Add(SqlExpression expression) =>
+      columnList.Add(expression is SqlColumn column ? column : SqlDml.ColumnRef(SqlDml.Column(expression)));
+
+    /// <summary>
+    /// Builds a <see cref="SqlColumnRef"/> by the specified <paramref name="expression"/> and
+    /// <paramref name="alias"/>; then adds it to the end of the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    /// <exception cref="ArgumentNullException"><paramref name="alias"/> is <c>null</c>.</exception>
+    public void Add(SqlExpression expression, string alias)
     {
-      ArgumentValidator.EnsureArgumentNotNull(columnReference, "columnReference");
-      base.Add(columnReference);
+      ArgumentValidator.EnsureArgumentNotNull(alias, nameof(alias));
+      columnList.Add(SqlDml.ColumnRef(SqlDml.Column(expression), alias));
     }
 
+    /// <summary>
+    /// Builds a <see cref="SqlColumnRef"/> by the specified <paramref name="expression"/> and <paramref name="alias"/>
+    /// then inserts it into <see cref="SqlColumnCollection"/> at the specified <paramref name="index"/>.
+    /// </summary>
+    /// <exception cref="ArgumentNullException"><paramref name="alias"/> is <c>null</c>.</exception>
+    /// <exception cref="IndexOutOfRangeException"><paramref name="index"/> is less than <c>0</c>.
+    /// -or- <paramref name="index"/> is greater than <see cref="Count"/>.</exception>
     public void Insert(int index, SqlExpression expression, string alias)
     {
-      ArgumentValidator.EnsureArgumentNotNull(alias, "alias");
-      Insert(index, SqlDml.ColumnRef(SqlDml.Column(expression), alias));
+      ArgumentValidator.EnsureArgumentNotNull(alias, nameof(alias));
+      columnList.Insert(index, SqlDml.ColumnRef(SqlDml.Column(expression), alias));
     }
 
+    /// <summary>
+    /// Adds <paramref name="columns"/> to the end of the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    /// <param name="columns">Columns to be added.</param>
     public void AddRange(params SqlColumn[] columns)
     {
-      ArgumentValidator.EnsureArgumentNotNull(columns, "columns");
-      foreach (SqlColumn c in columns) {
-        ArgumentValidator.EnsureArgumentNotNull(c, "column");
-        base.Add(c);
-      }
+      ArgumentValidator.EnsureArgumentNotNull(columns, nameof(columns));
+      columnList.AddRange(columns);
     }
 
-    public void AddRange<TColumn>(IEnumerable<TColumn> columns)
-      where TColumn : SqlColumn
-    {
-      ArgumentValidator.EnsureArgumentNotNull(columns, "columns");
-      foreach (TColumn c in columns)
-        base.Add(c);
-    }
+    /// <summary>
+    /// Adds <paramref name="columns"/> to the end of the <see cref="SqlColumnCollection"/>.
+    /// </summary>
+    /// <param name="columns">Columns to be added.</param>
+    /// <typeparam name="TColumn">A type of the columns in the specified <paramref name="columns"/>
+    /// collection; it must be <see cref="SqlColumn"/> or its inheritor.</typeparam>
+    public void AddRange<TColumn>(IEnumerable<TColumn> columns) where TColumn : SqlColumn =>
+      columnList.AddRange(columns);
+
+    /// <inheritdoc cref="ICollection{T}.Contains"/>
+    public bool Contains(SqlColumn item) => columnList.Contains(item);
+
+    /// <inheritdoc cref="ICollection{T}.CopyTo"/>
+    public void CopyTo(SqlColumn[] array, int arrayIndex) => columnList.CopyTo(array, arrayIndex);
+
+    /// <inheritdoc cref="ICollection{T}.Remove"/>
+    public bool Remove(SqlColumn item) => columnList.Remove(item);
 
+    /// <inheritdoc cref="ICollection{T}.Clear"/>
+    public void Clear() => columnList.Clear();
 
     // Constructors
 
@@ -91,14 +135,15 @@ public void AddRange<TColumn>(IEnumerable<TColumn> columns)
     /// </summary>
     public SqlColumnCollection()
     {
+      columnList = new List<SqlColumn>();
     }
 
     /// <summary>
     /// Initializes new instance of this type.
     /// </summary>
-    public SqlColumnCollection(IList<SqlColumn> list)
-      : base(list)
+    public SqlColumnCollection(IReadOnlyList<SqlColumn> list)
     {
+      columnList = new List<SqlColumn>(list);
     }
   }
 }