I'm new at c# .Net and I'm working to develop c# winform application. I need your help.
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```
public partial class Form1 : Form 
{ 
    OleDbConnection baglanti = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Burak YEŞİLYURT\Desktop\secret.accdb"); 
    OleDbCommand komutcu; 
    OleDbDataAdapter adpt; 
    DataSet ds; 
    public Form1() 
    { 
        InitializeComponent(); 
        baglanti.Open(); 
        OleDbCommand komutcu = new OleDbCommand("SELECT * FROM todo", baglanti); 
        OleDbDataAdapter adpt = new OleDbDataAdapter(komutcu); 
        DataSet ds = new DataSet(); 
        adpt.Fill(ds); 
        dataGridView1.DataSource = ds.Tables[0]; 

    } 

    private void button1_Click(object sender, EventArgs e) 
    { 
        OleDbCommandBuilder komut = new OleDbCommandBuilder(adpt); 
        DataSet yeni = new DataSet(); 
        yeni = ds.GetChanges(DataRowState.Modified); //here i get the error
        adpt.Update(yeni.Tables[0]); 
    } 
} 

```

---

When I debug my program, I get the following error at `yeni = ds.GetChanges(DataRowState.Modified);`

> 
> "Object reference not set to an instance of an object. " 
> 
> 
> 

My purpose: After filling `DataGridView` and user editing cell, save changes at cell.
I'm unable to solve this. Any help is welcome.
Thanks.