Object reference not instance of an object treeview in WPF?

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C#

WPF

LINQ

DataTable

How to var sql command variable convert to datatable variable.

How to query convert to datatable treeview item.
For example:

items[Name]
items[Surname]

I want to take the fields related to the query and keep them in the datatable and throw it in the treeview item. But I want to add the datatable, but it gets empty. How can I add.

Forexample:

Name Surname
Alex J
Michael K

items is 2 value. (Alex J and Michael K) But not set treeview item.object reference not instance of an object


Note: I want to this line DataTable but not convert to Datatable because error is red.
foreach(var items in query);

I want to

foreach(DataTable items in query);

What I have tried:

VMStudent.cs

public void GetStudents(){
var query="";   //linq queries
DataTable newTbl=new DataTable();
newTbl.Columns.Add("Name");
newTbl.Columns.Add("Surname");
foreach(var items in query);   
{
   newTbl.Rows.Add(items);
   Students std=new Students();
   std.Name=items["Name"].ToString();   // items is error and red color.
   std.Surname=items["SurnameName"].ToString(); // items is error and red color.
   StudentList.Add(std);

2.way try 


   newTbl.Rows.Add(items);
   Students std=new Students();
   std.Name="Name".ToString();   
   std.Surname=items"Surname".ToString(); //  name and surname is equal to not values.Equals is Name=Name and Surname=surname 
   StudentList.Add(std);

}
}



StudentsCall.cs


StudentList=GetStudents(); object reference not instance of an object

Student.cs

private string Name;
private string Surname