.Net 下ProgressBar控件可以让程序在加载数据时让用户知道目前的进度.诸如安装程序,加载数据到Listview中等.下面就以ProgressBar控件在Listview下的应用为例.

1.拖一个ProgressBar,一个ListView,一个Button到Winform中.我将ProgressBar命名为progBarReport,ListView命名为lvRentList,Button命名为btnSearch
2.界面部分(红色框部分为此例中用到的控件)

3.编辑代码部分
初始化ListView如:

private void initialListView()
{
            lvRentList.Columns.Add("租赁编号", 60);
            lvRentList.Columns.Add("会员编号", 60);
            lvRentList.Columns.Add("租赁金额", 70);
            lvRentList.Columns.Add("折扣率", 70);
            lvRentList.Columns.Add("总金额", 70);
            lvRentList.Columns.Add("租赁日期", 120);
            lvRentList.GridLines = true;
            lvRentList.View = View.Details;
            lvRentList.FullRowSelect = true;
        }

在申明部分创建个委托(delegate)

private delegate void dispProgStatus(string state);

用于更新ProgressBar的method.其中参数 state用于显示进度(当前及总共)

private void showProgStatus(string state)
{
string type = "";
if (progBarReport.InvokeRequired)
                progBarReport.Invoke(new dispProgStatus(showProgStatus), state);
else
{
                type = state.Substring(0, state.IndexOf("") + 2);
string[] data = state.Substring(state.IndexOf("") + 3).Split('/');
int current = 0;
                Int32.TryParse(data[0], out current);
int total = 0;
                Int32.TryParse(data[1], out total);
                progBarReport.Value = current;
                progBarReport.Maximum = total;
            }
if (lblProgStatus.InvokeRequired)
                lblProgStatus.Invoke(new dispProgStatus(showProgStatus), state);
else
                lblProgStatus.Text = state;
        }

载入数据到ListView中的method 其中参数DataTable dtRent是用于传递要载入到ListView中的数据

private void loadRentListView(DataTable dtRent,string state)
{
            lvRentList.Items.Clear();
            ArrayList memberList = new ArrayList();
decimal rentTotal = 0M;
            ArrayList itemList = new ArrayList();
string type = state.ToString();
ListViewItem[] rentItems = new ListViewItem[dtRent.Rows.Count]; //将用于整体插入ListView中可以大幅提高效率
for (int i = 0; i < dtRent.Rows.Count; i++)
{
if (i == dtRent.Rows.Count - 1)
                    type = "Loading Data Completed";
                state = type + (i + 1).ToString() + "/" + dtRent.Rows.Count.ToString();

int sessionID = 0;
                Int32.TryParse(dtRent.Rows[i].ItemArray.GetValue(0).ToString(), out sessionID);

int mid = 0;
                Int32.TryParse(dtRent.Rows[i].ItemArray.GetValue(1).ToString(), out mid);
if (!memberList.Contains(mid))
                    memberList.Add(mid);
                Decimal discount = 0M;
                Decimal.TryParse(dtRent.Rows[i].ItemArray.GetValue(3).ToString(), out discount);
                discount = Decimal.Round(discount * 100M, 2);
                Decimal total = 0M;
                Decimal.TryParse(dtRent.Rows[i].ItemArray.GetValue(4).ToString(), out total);
                rentTotal += total;
                DateTime rentDate = DateTime.Now;
                DateTime.TryParse(dtRent.Rows[i].ItemArray.GetValue(6).ToString(), out rentDate);

string[] items = { sessionID.ToString(), mid.ToString(), "$" + dtRent.Rows[i].ItemArray.GetValue(2).ToString(), "$" +discount.ToString() + "%"
                    , "$" + total.ToString(), rentDate.ToShortDateString() };
rentItems[i] = new ListViewItem(items) //将每条数据载入到ListViewItem中
showProgStatus(state.ToString()); //用于显示ProgressBar的进度
            }
lvRentList.Items.AddRange(rentItems); //批量插入数据到List View中,曾经试验过Add 比 AddRange的效率低百倍

            txtRentItemCount.Text = itemList.Count.ToString();
            txtRentMemberCount.Text = memberList.Count.ToString();
            txtRentFeeCount.Text = "$" + rentTotal.ToString();
        }

取出数据并调用载入数据到ListView的method其中参数object ThreadPool的静态method所要传递的参数,可以用来封装数据,未方便我基本用来传递进度

private void dispRentReport(object state)
{
            DateTime startDate = dtpStartDate.Value.Date;
            DateTime endDate = dtpEndDate.Value.Date.AddDays(1);
            Session mySession = new Session();
            dtRent = mySession.getSessionsByDate(startDate, endDate, 0);

            loadRentListView(dtRent,state.ToString());
        }

按钮btnSearch的click事件 点击按钮后即查找并将数据载入到ListView中

private void btnSearch_Click(object sender, EventArgs e)
{
            Console.WriteLine("Cat Index:" + comboSearchCat.SelectedIndex);
//Date Range
if (comboSearchCat.SelectedIndex == -1)
{
object state = "Loading Rent Data";
                ThreadPool.QueueUserWorkItem(dispRentReport, state);
            }
else
{
object state = "Loading Items under Category ";
                ThreadPool.QueueUserWorkItem(dispRentReportByCategory, state);
            }
            btnSearch.Enabled = false;
        }

运行结果如图: (图1 正在加载数据,并可以看到ListView中为空白.图2 显示数据加载完毕后才加载到ListView中)

(图1)