Add data to the text box to record in the dataGridView

After entering the information, click Add to add data to the dataGridView

        private void btnSend_Click(object sender, EventArgs e)
        {
            dataGridView1.ColumnCount = 4;
            dataGridView1.ColumnHeadersVisible = true;


            //避免重复输入多个编号
            if (dataGridView1.Rows.Count > 0)
            {
                for (int i = 0; i < dataGridView1.Rows.Count-1; i++)
                {
                    if (dataGridView1.Rows[i].Cells["dg_Item"].Value.ToString() == cob_Item.Text.Trim().ToString())
                    {
                        ErrorMSG(cob_Item.Text + " 已存在！");
                        return;
                    }
                }
            }    
            //textbox 的值输入到 datagridview
            if (cob_Type.Text.Trim() != "" & txtSN.Text.Trim() != ""& cob_Item.Text.Trim() != "" & txt_ItemValue.Text.Trim() != "" )
            {
                dataGridView1.Rows.Add(cob_Type.Text.Trim(),txtSN.Text.Trim(),cob_Item.Text.Trim(), txt_ItemValue.Text.Trim());
            }
        }