演员表 <object> 列表 <myclass> C＃

Question

By this code I got list of selected rows in AspxGrid.

string[] fieldName = new string[] { "UserId", "Name", "Address" };
List<object> SelectedList = Grid.GetSelectedFieldValues(fieldName);

Now I want to perform one of the below operation.

1. Filter this List of object by userid where userid = 1 using linq
2. Cast this List<object> into List<Users>

I have tried following two methods but Exception occurs.

Unable to cast object of type 'System.Object[]' to type 'CubeDataObject.Claims'.

List<Users> mylist = (List<Users>)(Object)SelectedList;
List<Users> listd = SelectedList.Select(n => (Users)n).ToList();

I have also tried so many other methods too but tired.

Answer 1

For this simple tast the Cast -extension-method on Enumerable exists:

var myList = SelectedList.Cast<User>();

Now you can easily filter:

var result = myList.Where(x => x.userId == 1);

Answer 2

It seems that you have list of boxed object[] . So, you need to unbox it and get the values of UserId , Name , Address by its corresponding index.
Here is example:

List<Users> mylist = SelectedList
    .Where(item => (int)((object[])item)[0] == 1)
    .Select(item =>
    {
        var values = (object[])item;

        return new Users()
        {
            UserId = (int)values[0],
            Name = (string)values[1],
            Address = (string)values[2]
        };
    })
    .ToList();

Answer 3

Linq has a special method for casting lists:

List<Users> mylist = SelectedList.Cast<Users>().Where(u => u.userid == 1).ToList();

This should work, assuming the objects are actually castable to a Users object.