public partial class FrmMain : Form
    {
        private SqlConnection sqlConn;

        public FrmMain()
        {
            InitializeComponent();
            sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["sqlConn"].ConnectionString);
        }

        private void btnSearchUser_Click(object sender, EventArgs e)//查询
        {
            StringBuilder strSql = new StringBuilder("select * from test where 1=1 ");

            if (!string.IsNullOrEmpty(txtGonoSelect.Text))
            {
                strSql.Append(" and gono='" + txtGonoSelect.Text.Replace("'", "''") + "'");
            }

            if (!string.IsNullOrEmpty(txtNameSelect.Text))
            {
                strSql.Append(" and name='" + txtNameSelect.Text.Replace("'", "''") + "'");
            }

            using (SqlDataAdapter da = new SqlDataAdapter(strSql.ToString(), sqlConn))
            {
                DataTable dt = new DataTable();
                da.Fill(dt);
                dgvSelect.DataSource = dt;

            }
        }

        private void btnInsertUser_Click(object sender, EventArgs e)//新增
        {
            if (string.IsNullOrEmpty(txtGonoInsert.Text))
            {
                MessageBox.Show("工号信息不能为空！", "系统提示：", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }

            using (SqlCommand cmd = new SqlCommand())
            {               
                cmd.Connection = sqlConn;
                 = CommandType.Text;
                 = "insert into test(gono,name) values(@gono,@name)";
                cmd.Parameters.Add("@gono", SqlDbType.Char, 6).Value = txtGonoInsert.Text.Replace("'", "''");
                cmd.Parameters.Add("@name", SqlDbType.Char, 10).Value = txtNameInsert.Text.Replace("'", "''");

                try
                {
                    sqlConn.Open();
                    cmd.ExecuteNonQuery();
                }
                catch (SqlException)
                {
                    throw new ApplicationException();
                }
                finally
                {
                    sqlConn.Close();
                }

                dgvInsert.DataSource = userInfoGet();
            }           
        }

        private DataTable userInfoGet()
        {
            SqlDataAdapter da = new SqlDataAdapter("select id,gono,name from test", sqlConn);
            DataTable dt = new DataTable();
            da.Fill(dt);

            return dt;
        }

        private void btnUserDelete_Click(object sender, EventArgs e)//删除
        {
            if (dgvDelete.SelectedRows.Count == 0)
            {
                MessageBox.Show("请选择要删除的行！");
                return;
            }

            foreach (DataGridViewRow dr in dgvDelete.SelectedRows)
            {
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.Connection = sqlConn;
                     = CommandType.Text;
                     = "delete from test where id='"+ dr.Cells["idDelete"].Value +"'";

                    try
                    {
                        sqlConn.Open();
                        cmd.ExecuteNonQuery();
                    }
                    catch (SqlException)
                    {
                        throw new ApplicationException();
                    }
                    finally
                    {
                        sqlConn.Close();
                    }
                }
            }

            dgvDelete.DataSource = userInfoGet();
        }

        private void btnSelect_Click(object sender, EventArgs e)//1
        {
            tbMain.SelectedIndex = 1;
        }

        private void btnInsert_Click(object sender, EventArgs e)//2
        {
            tbMain.SelectedIndex = 2;
        }

        private void btnUpdate_Click(object sender, EventArgs e)//3
        {
            tbMain.SelectedIndex = 3;
            dgvUpdate.DataSource = userInfoGet();
        }       

        private void btnDelete_Click(object sender, EventArgs e)//4
        {
            dgvDelete.DataSource = userInfoGet();
            tbMain.SelectedIndex = 4;
        }

        private void dgvUpdate_CellDoubleClick(object sender, DataGridViewCellEventArgs e)//更新
        {
            string id = dgvUpdate.CurrentRow.Cells["idUpdate"].Value.ToString();
            string gono = dgvUpdate.CurrentRow.Cells["gonoUpdate"].Value.ToString();
            string name = dgvUpdate.CurrentRow.Cells["nameUpdate"].Value.ToString();
            string returnBlag = string.Empty;

            using (FrmUserUpdate frmUserUpdate = new FrmUserUpdate(id, gono, name, sqlConn))
            {
                frmUserUpdate.ShowDialog(this);
                returnBlag = frmUserUpdate.ReturnBlag;
            }

            if (returnBlag == "Confirm")
            {
                //dgvUpdate.DataSource = userInfoGet();
            }
            dgvUpdate.DataSource = userInfoGet();
        }

这也太多了吧
你标注一下哪几句看不懂

不少。。

                dgvInsert.DataSource = userInfoGet();//绑定数据显示出来

                SqlDataAdapter da = new SqlDataAdapter("select id,gono,name from test order by id desc", sqlConn);
                DataTable dt = new DataTable();
                da.Fill(dt);
                dgvInsert.DataSource = dt;