如何在会话中保存SQL查询以供以后使用
本文关键字：查询 SQL 会话 保存 | 更新日期: 2023-09-27 18:18:15
我有一个函数，每次按下按钮或每次更改7个下拉列表中的任何一个选择时运行查询。我怎么能改变现有的方法来使用会话或ViewState，所以我的页面将运行查询一次，然后对会话或ViewState查询，而不是出去到我的SQL服务器的每个请求?
后台代码:
protected void Page_Load(object sender, EventArgs e)
{
strMainQuery = @"SELECT 'http://dddfgdgdfg?objectid=' + CT.OBJECTID + '&classid=1224' 'Task Detail'
,LTRIM(RTRIM(CT.ATTR2846)) 'Service'
,LTRIM(RTRIM(CT.ATTR2812)) 'Status'
,CONVERT(VARCHAR(14), CT.ATTR2752, 110) 'Due Date'
,LTRIM(RTRIM(CT.ATTR2739)) 'Task Name'
,LTRIM(RTRIM(UA.REALNAME)) 'Owner'
,LTRIM(RTRIM(CT.ATTR2799)) 'Client'
FROM HSI.RMOBJECTINSTANCE1224 CT INNER JOIN HSI.RMOBJECTINSTANCE1232 S ON CT.ATTR2846 = S.ATTR2821 INNER JOIN HSI.USERACCOUNT UA ON S.FK2852 = (UA.USERNUM * -1)";
if (!Page.IsPostBack)
{
ViewState["sortOrder"] = "Asc";
ViewState["sortExp"] = "Due Date";
PullData("Due Date", "Asc"); //ASC: A (top) to Z (bottom) || # (low to high) || Date (oldest to newest)
}
else
{
PullData(ViewState["sortExp"].ToString(), ViewState["sortOrder"].ToString());
}
}
public void PullData(string sortExp, string sortDir)
{
string query = "";
DataTable taskData = new DataTable();
connString = ""; //connection string
if (ddlTaskName.SelectedIndex > 0)
{
strClause += " AND CT.ATTR2739 = '" + ddlTaskName.SelectedItem.Text + "'";
}
else
{
strClause += " AND CT.ATTR2739 LIKE '%'";
}
if (ddlService.SelectedIndex > 0)
{
strClause += " AND CT.ATTR2846 = '" + ddlService.SelectedItem.Text + "'";
}
else
{
strClause += " AND CT.ATTR2846 LIKE '%'";
}
if (ddlStatus.SelectedIndex > 0)
{
strClause += " AND CT.ATTR2812 = '" + ddlStatus.SelectedItem.Text + "'";
}
else
{
strClause += " AND CT.ATTR2812 LIKE '%'";
}
if (ddlDueDate.SelectedIndex > 0)
{
strClause += " AND CONVERT(VARCHAR(14), CT.ATTR2752, 110) = '" + ddlDueDate.SelectedItem.Text + "'";
}
else
{
strClause += " AND CONVERT(VARCHAR(14), CT.ATTR2752, 110) LIKE '%'";
}
if (ddlOwner.SelectedIndex > 0)
{
strClause += " AND UA.REALNAME = '" + ddlOwner.SelectedItem.Text + "'";
}
else
{
strClause += " AND UA.REALNAME LIKE '%'";
}
if (ddlClient.SelectedIndex > 0)
{
strClause += " AND CT.ATTR2799 = '" + ddlClient.SelectedItem.Text + "'";
}
else
{
strClause += " AND CT.ATTR2799 LIKE '%'";
}
if (ddlTaskName.SelectedIndex == 0 && ddlService.SelectedIndex == 0 && ddlStatus.SelectedIndex == 0 && ddlDueDate.SelectedIndex == 0 && ddlOwner.SelectedIndex == 0 && ddlClient.SelectedIndex == 0)
{
query = strMainQuery + " WHERE CT.ACTIVESTATUS = 0";
}
else
{
query = strMainQuery + " WHERE CT.ACTIVESTATUS = 0" + strClause;
}
using (SqlConnection conn = new SqlConnection(connString))
{
try
{
SqlCommand cmd = new SqlCommand(query, conn);
// create data adapter
SqlDataAdapter da = new SqlDataAdapter(query, conn);
// this will query your database and return the result to your datatable
DataSet myDataSet = new DataSet();
da.Fill(myDataSet);
DataView myDataView = new DataView();
myDataView = myDataSet.Tables[0].DefaultView;
if (sortExp != string.Empty)
{
//MessageBox.Show(sortExp);
//MessageBox.Show(sortDir);
myDataView.Sort = string.Format("{0} {1}", sortExp, sortDir);
}
yourTasksGV.DataSource = myDataView;
yourTasksGV.DataBind();
TasksUpdatePanel.Update();
conn.Close();
}
catch (Exception ex)
{
string error = ex.Message;
}
}
}
正如你所看到的，每次PullData被调用时，它都会出去到SQL服务器并运行查询，一旦我开始有越来越多的数据，查询最终会变慢。
如何将现有方法转换为查询一次并保存到会话/ViewState，这样我就不必每次都对SQL服务器进行查询了?
执行查询前，请检查缓存。如果有，就使用它。如果没有，则运行查询并将结果数据添加到Cache中。
你可以使用缓存。插入方法(String, Object, CacheDependency, DateTime, TimeSpan)。您可以找到一些很棒的缓存技巧:. NET缓存:技术和最佳实践。
下面是我将如何构建PullData方法:public void PullData(string sortExp, string sortDir)
{
// build your query string
// ...
// Now create a hash of that query string
string cacheKey = HashHelper(query);
DataSet ds = null;
// check cache if key exists
if(Cache[cacheKey] != null)
{
// read dataset from cache
ds = (DataSet)Cache[cacheKey];
}
else
{
// perform sql command and fill your dataset
// ....
// save dataset to cache for 30 minutes or whatever you like
Cache.Insert(cacheKey, ds, null, DateTime.Now.AddMinutes(30), TimeSpan.Zero);
}
// Get DataView based on sort options
DataView myDataView = new DataView();
myDataView = ds.Tables[0].DefaultView;
if (sortExp != string.Empty)
{
myDataView.Sort = string.Format("{0} {1}", sortExp, sortDir);
}
yourTasksGV.DataSource = myDataView;
yourTasksGV.DataBind();
TasksUpdatePanel.Update();
// keep calm and carry on
}
这是我的哈希助手
private string HashHelper(string query)
{
using (SHA256Managed hashEngine = new SHA256Managed())
{
byte[] data = hashEngine.ComputeHash(Encoding.UTF8.GetBytes(query));
StringBuilder hash = new StringBuilder(64);
for (int i = 0; i < data.Length; i++)
{
hash.Append(data[i].ToString("x2"));
}
return hash.ToString();
}
}
以你目前的代码结构，你做不到。因为您的strMainQuery具有没有WHERE子句的sql语句，并且随着下拉值的变化，您正在动态构建WHERE子句的条件。所以你不能在会话中存储结果集，因为每个下拉选择的值都会改变。
你可以这样做。
-
检索
strMainQuery的所有记录，不带任何WHERE条件，并将结果存储在会话或其他状态管理中。所以你的PullData方法将包含SqlCommand cmd = new SqlCommand(strMainQuery, conn); -
随着下拉值的变化，访问会话对象并使用LINQ根据不同下拉值过滤数据。这至少可以帮助您避免每次下拉值更改都访问数据库服务器，而不是
读取一次=>存储=>并使用LINQ进行额外的数据过滤
在下面的行中绑定网格之前，进行数据过滤。
// do the data filtering against the data source based on dropdown selected values yourTasksGV.DataSource = myDataView; yourTasksGV.DataBind();
我确实看到您在!Page.IsPostBack以及else部分的PageLoad中调用PullData，这意味着每次由页面上的任何其他控件触发回发时都会调用此函数PullData。而是为下拉菜单添加一个OnSelectedIndexChanged事件并调用PullData方法。