Я получаю ошибку on (int v2 = cmd1.executenonquery(); ) [system.data.oledb.oledbexception: 'нет значения для одного или нескольких обязательных параметров.']

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public partial class Form1 : Form

    {
        OleDbConnection con1 = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\User\Desktop\mmA.accdb");
        int count1 = 0;
        OleDbConnection con2 = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\User\Desktop\MA.accdb");
        int count2 = 0;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string a = Convert.ToString(textBox1.Text);
            label2.Text = textBox1.Text.Substring(a.Length - 1);
            label1.Text = textBox1.Text.Remove(a.Length - 1, 1);

            count1 = 0;
            con1.Open();
            OleDbCommand cmd1 = con1.CreateCommand();
            cmd1.CommandType = CommandType.Text;
            cmd1.CommandText = "select * from Table1 where mmA='" + label1.Text + "'";
            int v1 = cmd1.ExecuteNonQuery();
            DataTable dt1 = new DataTable();
            OleDbDataAdapter Da1 = new OleDbDataAdapter(cmd1);
            Da1.Fill(dt1);
            count1 = Convert.ToInt32(dt1.Rows.Count.ToString());
            dataGridView1.DataSource = dt1;
            con1.Close();

            count2 = 0;
            con2.Open();
            OleDbCommand cmd2 = con2.CreateCommand();
            cmd2.CommandType = CommandType.Text;
            cmd2.CommandText = "select * from Table4 where MA='" + label2.Text + "'";
            int v2 = cmd1.ExecuteNonQuery();
            DataTable dt2 = new DataTable();
            OleDbDataAdapter Da2 = new OleDbDataAdapter(cmd2);
            Da2.Fill(dt2);
            count2 = Convert.ToInt32(dt2.Rows.Count.ToString());
            dataGridView2.DataSource = dt2;
            con2.Close();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // TODO: This line of code loads data into the 'mADataSet.Table4' table. You can move, or remove it, as needed.
            this.table4TableAdapter.Fill(this.mADataSet.Table4);
            // TODO: This line of code loads data into the 'mmADataSet.Table1' table. You can move, or remove it, as needed.
            this.table1TableAdapter.Fill(this.mmADataSet.Table1);

        }

        private void dataGridView1_CellEnter(object sender, DataGridViewCellEventArgs e)
        {
            if (dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value != null)
            {
                dataGridView1.CurrentRow.Selected = true;
                textBox2.Text = dataGridView1.Rows[e.RowIndex].Cells["mmA"].FormattedValue.ToString();
                textBox3.Text = dataGridView1.Rows[e.RowIndex].Cells["cm3A"].FormattedValue.ToString();
            }
        }

        private void dataGridView2_CellEnter(object sender, DataGridViewCellEventArgs e)
        {
            if (dataGridView2.Rows[e.RowIndex].Cells[e.ColumnIndex].Value != null)
            {
                dataGridView2.CurrentRow.Selected = true;
                textBox5.Text = dataGridView2.Rows[e.RowIndex].Cells["MA"].FormattedValue.ToString();
                textBox6.Text = dataGridView2.Rows[e.RowIndex].Cells["CMA"].FormattedValue.ToString();
            }
        }

    }

Что я уже пробовал:

пожалуйста, скажи мне, что я делаю не так.Заранее спасибо!

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