c# - 为什么 LINQ 无法将 DataRows 添加到 DataTable？

Question

为了将 ExpandoObjects 塞进网格中，进行了以下两次尝试。

这行不通:

var data = _d.Query<dynamic>(_script);         // returns IEnumerable<ExpandoObject>

IDictionary<string, object> c = (IDictionary<string, object>)data.FirstOrDefault();
DataTable dt = new DataTable();

dt.BeginLoadData();
dt.Columns.AddRange(c.Keys.Select(k => new DataColumn(k)).ToArray());
data.Select(r => dt.Rows.Add((r as IDictionary<string, object>).Values.ToArray()));
dt.EndLoadData();

但是这样做:

dt.Columns.AddRange(c.Keys.Select(k => new DataColumn(k)).ToArray());
foreach (IDictionary<string, object> r in data)
  dt.Rows.Add(r.Values.ToArray());

为什么？

Answer 1

选择方法

The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

所以这个选择永远不会被执行:

data.Select(r => dt.Rows.Add((r as IDictionary<string, object>).Values.ToArray()));

引用 http://msdn.microsoft.com/ru-ru/library/bb548891.aspx