泛型类型的Linq类型转换

Question

我找到了这个代码,但即使我尝试了很多转换后它也无法运行.基本上它巧妙地将Datatable转换为可序列化的List.

错误是它无法将a转换Dictionary<string, object>为List<object>:

public GridBindingData GetSomething() {

DataTable dt = GetDatatable();

var columns = dt.Columns.Cast<System.Data.DataColumn>();

var data = dt.AsEnumerable()
    .Select(r => columns.Select(c => new { Column = c.ColumnName, Value = r[c] })
    .ToDictionary(i => i.Column, i => i.Value != System.DBNull.Value ? i.Value : null))
    .ToList<object>();

return new GridBindingData() { Data = data , Count = dt.Rows.Count };
}

我尝试了很多转换,包括:

List<object> newdata = (List<object>)data.AsEnumerable().Cast<object>();

基本上,GridBindingData的Data属性必须有List<object>.那可能吗？

Answer 1

嗯.要看到你得到的错误并不容易,但也许你需要.Cast<object>().ToList():

var data = dt.AsEnumerable()
    .Select(r => columns.Select(c => new { Column = c.ColumnName, Value = r[c] })
    .ToDictionary(i => i.Column, i => i.Value != System.DBNull.Value ? i.Value : null))
    .Cast<object>()
    .ToList();

编辑这应该完美无缺,在REPL中测试:

csharp> new Dictionary<string, string> { {"key","value"} }.ToList().Cast<object>();
{ [key, value] }

csharp> new Dictionary<string, string> { {"key","value"} }.Cast<object>().ToList();               
{ [key, value] }