How to put values from DataReader into List<T>? [duplicate]

This question already has answers here: Closed 10 years ago.

Possible Duplicate:

How can I easily convert DataReader to List<T>?

I want to put the data 开发者_如何学JAVAwhich is coming from datareader object in a generic list. I have done like this but it doesn't work...

I am getting cast exception error in foreach row!

 SqlDataReader pointreader = cmd2.ExecuteReader();
 var pointt = new List<int>();
 while (pointreader.Read())
 {
     foreach (int item in pointreader)
     {
        pointt.Add(item);
         if (pointt.Contains(point))
         {
             matchpoint = item;
         }
     }
 }

---

SqlDataReader cannot be accessed in the way you have described as it does not implement IEnumerable. Instead you need to access each field individually:

SqlDataReader puanoku = cmd2.ExecuteReader();
List<int> puann = new List<int>();
while (puanoku.Read())
{
    for (int i = 0; i < puanoku.FieldCount; i++)
    {
        if (puanoku.GetFieldType(i) == typeof(int))
        {
            // Do something here
        }
    }
}

If you've only selected one column and are certain that it is an int then you can simplify the code like so:

SqlDataReader puanoku = cmd2.ExecuteReader();
List<int> puann = new List<int>();
while (puanoku.Read())
{
    int value = puanoku.GetInt32(1);

    // Do something with the int here...
}

This article may be of some use.

---

I think you need to get item from the Reader, like puanoku["item"] and convert it to int. Add then only you can add it to the list.

while(Reader.Read())
{
  var myId = (int)Reader["myId"];
  myIdList.Add(myId); // or you can do myIdList.Add(int)Reader["myId"]);
}

---

The datareader is a pointer to rows in a table. You can get to the individual attributes using an indexer on the reader and use the FieldCount property to obtain the values.

 while (puanoku.Read())
 {
  for(int i = 0; i < puanoku.FieldCount)
  {
      puann.Add(puanoku.GetInt32(i));
  }
 }

If you only want unique values you should use a HashSet rather than a List since it will test for existence in O(1) rather than O(n).