System windows forms datagridviewcell value get вернул null

How Can Fixed This Error When return null

This is the relevant code part:

        private void DgvIncome_MouseClick(object sender, MouseEventArgs e)
        {

            //try
            {
                txtCode.Text = dgvIncome.SelectedRows[0].Cells[1].Value.ToString();
                txtRecNo.Text = dgvIncome.SelectedRows[0].Cells[2].Value.ToString();
                txtMembershipID.Text = dgvIncome.SelectedRows[0].Cells[3].Value.ToString();
                txtGustName.Text = dgvIncome.SelectedRows[0].Cells[4].Value.ToString();
                txtGustMobile.Text = dgvIncome.SelectedRows[0].Cells[5].Value.ToString();
                txtNote.Text = dgvIncome.SelectedRows[0].Cells[6].Value.ToString();
                txtSalesNo.Text = dgvIncome.SelectedRows[0].Cells[7].Value.ToString();
                txtMainPackageNo.Text = dgvIncome.SelectedRows[0].Cells[8].Value.ToString();
                txtSubPackageNo.Text = dgvIncome.SelectedRows[0].Cells[9].Value.ToString();
                txtPackageNo.Text = dgvIncome.SelectedRows[0].Cells[10].Value.ToString();
                txtNatPrice.Text = dgvIncome.SelectedRows[0].Cells[11].Value.ToString();
                txtDiscount.Text = dgvIncome.SelectedRows[0].Cells[12].Value.ToString();
                dtpStartDate.Text = dgvIncome.SelectedRows[0].Cells[13].Value.ToString();
                dtpEndDate.Text = dgvIncome.SelectedRows[0].Cells[14].Value.ToString();
                ShowSalesName();
                ShowMainPackageName();
                ShowSubPackageName();
                ShowPackageName();
                ShowPrice();
                chbxSearch.Checked = false;
            }

Error: When select a row, there are empty values ,

System.NullReferenceException: 'Object reference not set to an instance of an object.'

System.Windows.Forms.DataGridViewCell.Value.get returned null.

Здесь мне нужно избегать null из datagridview (winform)

 private void SendUpdate()
        {
            
            if ((string)dataGridView1.SelectedRows[0].Cells[0].Value != string.Empty )
            {
                if (1 == dataGridView1.SelectedRows.Count)
                {
                    int Id = Convert.ToInt32(dataGridView1.SelectedRows[0].Cells[0].Value);
                    Update up = new Update();
                    up.AssignValue(Id);
                    up.textBox1.Text = dataGridView1.SelectedRows[0].Cells[1].Value.ToString();
                    up.comboBox1.Text = dataGridView1.SelectedRows[0].Cells[2].Value.ToString();
                    up.textBox2.Text = dataGridView1.SelectedRows[0].Cells[3].Value.ToString();
                    up.textBox3.Text = dataGridView1.SelectedRows[0].Cells[4].Value.ToString();
                    up.textBox4.Text = dataGridView1.SelectedRows[0].Cells[5].Value.ToString();
                    up.textBox5.Text = dataGridView1.SelectedRows[0].Cells[6].Value.ToString();
                    up.ShowDialog();
                }
                else
                {
                    MessageBox.Show("Please Select the Single Data Which Required to Update");
                }
            }
            else 
            {

                MessageBox.Show("You Select the empty Row");

            }
            
        }

Я пробовал !=string.empty;, !=null;, ! = «»;
но ошибка не решена.

1 == dataGridView1.SelectedRows.Count это правда

Но

(string)dataGridView1.SelectedRows[0].Cells[0].Value имеет нулевое значение
Показать ошибку

System.NullReferenceException: ‘Object reference not set to an instance of an object.’
System.Windows.Forms.DataGridViewCell.Value.get returned null.

        private void DgvIncome_MouseClick(object sender, MouseEventArgs e)
        {

            //try
            {
                txtCode.Text = dgvIncome.SelectedRows[0].Cells[1].Value.ToString();
                txtRecNo.Text = dgvIncome.SelectedRows[0].Cells[2].Value.ToString();
                txtMembershipID.Text = dgvIncome.SelectedRows[0].Cells[3].Value.ToString();
                txtGustName.Text = dgvIncome.SelectedRows[0].Cells[4].Value.ToString();
                txtGustMobile.Text = dgvIncome.SelectedRows[0].Cells[5].Value.ToString();
                txtNote.Text = dgvIncome.SelectedRows[0].Cells[6].Value.ToString();
                txtSalesNo.Text = dgvIncome.SelectedRows[0].Cells[7].Value.ToString();
                txtMainPackageNo.Text = dgvIncome.SelectedRows[0].Cells[8].Value.ToString();
                txtSubPackageNo.Text = dgvIncome.SelectedRows[0].Cells[9].Value.ToString();
                txtPackageNo.Text = dgvIncome.SelectedRows[0].Cells[10].Value.ToString();
                txtNatPrice.Text = dgvIncome.SelectedRows[0].Cells[11].Value.ToString();
                txtDiscount.Text = dgvIncome.SelectedRows[0].Cells[12].Value.ToString();
                dtpStartDate.Text = dgvIncome.SelectedRows[0].Cells[13].Value.ToString();
                dtpEndDate.Text = dgvIncome.SelectedRows[0].Cells[14].Value.ToString();
                ShowSalesName();
                ShowMainPackageName();
                ShowSubPackageName();
                ShowPackageName();
                ShowPrice();
                chbxSearch.Checked = false;
            }

System.NullReferenceException: 'Object reference not set to an instance of an object.'

System.Windows.Forms.DataGridViewCell.Value.get returned null.

1 ответ

Лучший ответ

txtCode.Text = dgvIncome.SelectedRows[0].Cells[1].Value?.ToString();

Есть дгв2, в котором находятся чекбоксы. По какой то причине, при попытке получить значение ячейки, я получаю ошибку.

Допустим, хочу посмотреть в содержимое ячейки вот так

private void Import_DoubleClick(object sender, EventArgs e)
        {
            MessageBox.Show(dataGridView2.Rows[0].Cells[0].Value.ToString());
        }

Получаю ошибку

System.NullReferenceException: "Ссылка на объект не указывает на экземпляр объекта."

System.Windows.Forms.DataGridViewCell.Value.get вернул null.

Юмор в том, что есть код, который обращается к дгв2 точно так же, и никаких проблем, работает всегда.
В нем я сохраняю дгв2 в бд.

private void button5_Click(object sender, EventArgs e)
        {
            string src = "0", upd = "0";
            if (radioButton1.Checked) src = "1";
            if (checkBox1.Checked) upd = "1";

            MySql.command($"UPDATE import SET link = '{MySql.escape(textBox2.Text)}', isupdate = '{upd}', source = '{src}', type = '{MySql.escape(comboBox1.Text)}', sklad = '{MySql.escape(comboBox2.Text)}', skip = '{textBox1.Text}', group_id = '{textBox3.Text}' WHERE name = '{MySql.escape(name)}'");

            MySql.command($"DELETE FROM import_ WHERE import_name = '{MySql.escape(name)}'");

            for (int i = 0; i < dataGridView3.Columns.Count; i++)
            {
                string combobox = "----------";
                if (dataGridView3.Rows[0].Cells[i].Value as string != null) combobox = dataGridView3.Rows[0].Cells[i].Value.ToString();

                MySql.command($"INSERT INTO import_ (columnindex, import_name, comboBox, checkBox) VALUES ('{i}','{MySql.escape(name)}','{MySql.escape(combobox)}','{dataGridView2.Rows[0].Cells[i].Value}')");
            }

            MessageBox.Show("Сохранено");
        }

Приведу еще код, который создает и заполняет все дгв.

private void loadGridsInfo()
        {
            var dt = MySql.getTable($"SELECT columnindex, comboBox, checkBox FROM import_ WHERE import_name = '{name}'");
            dt = dt.AsEnumerable().OrderBy(n => int.Parse(n[0].ToString())).CopyToDataTable();
            int count = dt.Rows.Count;
            int min;
            if (dataGridView1.Columns.Count < count) min = dataGridView1.Columns.Count;
            else                                     min = count;

            for (int i = 0; i < min ; i++)
            {
                if (dt.Rows[i][2].ToString() == "True") dataGridView2.Rows[0].Cells[i].Value = true;

                dataGridView3.Rows[0].Cells[i].Value = dt.Rows[i][1].ToString();
            }
        }

private void adaptGrids()
        {
            dataGridView2.Rows.Clear();
            dataGridView3.Rows.Clear();
            dataGridView2.Columns.Clear();
            dataGridView3.Columns.Clear();

            for (int i = 0; i < dataGridView1.Columns.Count; i++)
            {
                var clmn1 = new DataGridViewComboBoxColumn();
                var clmn2 = new DataGridViewCheckBoxColumn();

                clmn1.HeaderText = "C" + i;
                clmn2.HeaderText = "C" + i;
                clmn1.Width = dataGridView1.Columns[i].Width;
                clmn2.Width = dataGridView1.Columns[i].Width;
                clmn1.DataSource = comboBox;

                dataGridView2.Columns.Add(clmn2);
                dataGridView3.Columns.Add(clmn1);
            }
            dataGridView2.Rows.Add();
            dataGridView3.Rows.Add();
        }

Один из тех случаев, когда даже не знаю куда копать. Есть идеи?

 The exception is thrown at line if (bool.Parse(row.Cells[0].Value.ToString())).

 Exception details:

private void btnDeleteCategory_Click(object sender, EventArgs e)

{

foreach (DataGridViewRow row in CategoryGV.Rows)

{

if (bool.Parse(row.Cells[0].Value.ToString()))

{

string cs = ConfigurationManager.ConnectionStrings[«aladin»].ConnectionString;

SqlConnection con = new SqlConnection(cs);

SqlCommand cmd = new SqlCommand(«DELETE FROM lwpos_categories WHERE id= ‘» + Convert.ToInt32(row.Cells[1].Value) + «‘ «, con);

con.Open();

cmd.ExecuteNonQuery();

con.Close();

}

}

MessageBox.Show(«Deleted Successfully», «Successfull operation», MessageBoxButtons.OK, MessageBoxIcon.Information);

}

Here I need to avoid null from datagridview (winform)

 private void SendUpdate()
        {
            
            if ((string)dataGridView1.SelectedRows[0].Cells[0].Value != string.Empty )
            {
                if (1 == dataGridView1.SelectedRows.Count)
                {
                    int Id = Convert.ToInt32(dataGridView1.SelectedRows[0].Cells[0].Value);
                    Update up = new Update();
                    up.AssignValue(Id);
                    up.textBox1.Text = dataGridView1.SelectedRows[0].Cells[1].Value.ToString();
                    up.comboBox1.Text = dataGridView1.SelectedRows[0].Cells[2].Value.ToString();
                    up.textBox2.Text = dataGridView1.SelectedRows[0].Cells[3].Value.ToString();
                    up.textBox3.Text = dataGridView1.SelectedRows[0].Cells[4].Value.ToString();
                    up.textBox4.Text = dataGridView1.SelectedRows[0].Cells[5].Value.ToString();
                    up.textBox5.Text = dataGridView1.SelectedRows[0].Cells[6].Value.ToString();
                    up.ShowDialog();
                }
                else
                {
                    MessageBox.Show("Please Select the Single Data Which Required to Update");
                }
            }
            else 
            {

                MessageBox.Show("You Select the empty Row");

            }
            
        }

I had try !=string.empty; , !=null; , !="";
but error not solved.

1 == dataGridView1.SelectedRows.Count it true

But

(string)dataGridView1.SelectedRows[0].Cells[0].Value have null value
Show error

System.NullReferenceException: ‘Object reference not set to an instance of an object.’

System.Windows.Forms.DataGridViewCell.Value.get returned null.