Good day!
When I run the following code, I got an error(object reference not set to an instance of an object ) related to the line of code coloured with red shown in the code below:  
Can anyone please help me with this error
|  private void button2_Click(object sender, EventArgs e)
 {
 if (textBox2.Text == "" || textBox3.Text=="")
 {
 MessageBox.Show("?? ?? ?? ????? ??? ??????? ?????? ??????? ??? ????? ??? ?? ?????");
 return;
 }
 a.bindingSource2.EndEdit();
 a.???????TableAdapter.Update(a.cookbook1DataSet1.???????);
 a.bindingSource3.EndEdit();
 a.???????TableAdapter.Update(a.cookbook1DataSet1.???????);
 
 int xx = dataGridView1.Rows.Count - 1;
 for (int i = 0; i <= xx; i++)
 {
 
 // the error is here
 
 
 textBox7.Text = dataGridView1.Rows[i].Cells[0].Value.ToString();
 
 
 a.bindingSource4.EndEdit();
 a.????????TableAdapter.Update(a.cookbook1DataSet1.????????);
 a.bindingSource4.AddNew();
 textBox6.Text = textBox2.Text;
 
 }
 a.bindingSource2.AddNew();
 a.bindingSource3.AddNew();
 textBox4.Text = comboBox1.Text;
 
 }
 
 |