fill array from dataset

Question

I try to fill array from dataset. Firstly I am creating a class

public class BasvuruMaster
{
     public string Tarih { get; set; }
     public string Icerik { get; set; }
     public string RefNo { get; set; }
}

Secondly I am creating connection

I can connect to my database but I cannot fill my array.

public BasvuruMaster[] BasvuruListele(string TCK)
{
  string stm = "SELECT TARIH,ICERIK ,REFNO FROM TABLE WHERE TCK=@TCK";
  MySqlDataAdapter da = new MySqlDataAdapter(stm, cnn);
  da.SelectCommand.Parameters.AddWithValue("@TCK", TCK);
  DataSet ds = new DataSet();
  da.Fill(ds);
  BasvuruMaster[] BasVurList = new BasvuruMaster[ds.Tables[0].Rows.Count];
    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
    {
      if (ds.Tables.Count > 0)
      {
        BasVurList[i].Tarih = ds.Tables[0].Rows[i + 1].ItemArray[0].ToString();
        BasVurList[i].Icerik = ds.Tables[0].Rows[i+1].ItemArray[1].ToString();
        BasVurList[i].RefNo = ds.Tables[0].Rows[i+1].ItemArray[2].ToString();
      }
    } 
  return BasVurList;
}

What am I supposed to do?

The error message is

An exception of type 'System.NullReferenceException' occurred in WebApplication1.dll but was not handled in user code

Can we see the definition of `BasvuruMaster` as well? On which line you get this error? Also; [What is a `NullReferenceException` and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Soner Gönül, May 20 '15 at 13:48
BasVurList[i].Tarih = ds.Tables[0].Rows[i + 1].ItemArray[0].ToString(); this line has problem — Egemen HALICI, May 20 '15 at 13:51
Set a breakpoint. Inspect your dataset. Check the array indices. — DrKoch, May 20 '15 at 13:53
You are missing a BasVurList[i] = new BasvuruMaster() in your code. All entries in your Array will be null first (the default for a class). — Ralf, May 20 '15 at 13:54
You should exchange your `if`and `for`: first check if a table is available, then access it. — DrKoch, May 20 '15 at 13:54
I set. I can see "ds.Tables[0].Rows[i + 1].ItemArray[0]" but .tostring() doesn't work — Egemen HALICI, May 20 '15 at 13:55
@EgemenHALICI: Just for the sake of debug, check the filling process for one class attribute outside of the for loop... What does happen? — User, May 20 '15 at 13:57
I can read data from dataset when I debugging. The problem is .tostring(). — Egemen HALICI, May 20 '15 at 14:03
Firstly I wrote Rows[i] , but I couldn't access the data when I am debugging.After I chanced to Rows[i + 1]. Now I can read data but I cannot fill my array — Egemen HALICI, May 20 '15 at 14:04

Soner Gönül · Accepted Answer · 2015-05-20T14:11:17.627

I try to explain a little bit deeply.

From Arrays (C# Programming Guide)

The default values of numeric array elements are set to zero, and reference elements are set to null.

Since you have an array of BasvuruMaster (which is a class which is a reference type) all your elements are initalized to null. And since you try to acccess Tarih, Icerik and RefNo properties of a null value, that's why you get NullReferenceException.

You can initialize all your BasvuruMaster elements inside your for loop.

BasvuruMaster[] BasVurList = new BasvuruMaster[ds.Tables[0].Rows.Count];
for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
{
      if (ds.Tables.Count > 0)
      {
        BasVurList[i] = new BasvuruMaster(); <-- HERE
        BasVurList[i].Tarih = ds.Tables[0].Rows[i].ItemArray[0].ToString();
        BasVurList[i].Icerik = ds.Tables[0].Rows[i].ItemArray[1].ToString();
        BasVurList[i].RefNo = ds.Tables[0].Rows[i].ItemArray[2].ToString();
      }
}

With that line, you initialize your element with new BasvuruMaster() and it's properties initialized their default values. (since they are string, both Tarih, Icerik and RefNo will be null by default)

As Ralf pointed, I think your ds.Tables[0].Rows[i+1] should be ds.Tables[0].Rows[i] since you still try to increment after the last value, you will get index out of range exception.

Rows[i+1] will still be after the last row. And while you showing how to do it please place the if outside of the loop ;) — Ralf, May 20 '15 at 14:04
Thanks but I still problem.When I try to write thisway, I cannot build it. The message is The type or namespace name "BasvurList" could not be found (are you missing a using directive or an assembly reference?) — Egemen HALICI, May 20 '15 at 14:10
@EgemenHALICI Sorry. It should be `new BasvuruMaster()`. Fixed. — Soner Gönül, May 20 '15 at 14:11

fill array from dataset

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