ObservableCollection和SQlite到Async？ [英] ObservableCollection and SQlite to Async?
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问题描述
我对数据库和异步编程都很陌生。我正在制作一个POS应用程序，最终将有数百个客户，可能还有数千个交易。当我想进行客户搜索或查找上一张票时，我不希望我的程序
等待结果等待。
这是显示搜索结果：
<预类= "prettyprint">私人异步任务searchCritiria_TextChanging（文本框发件人，TextBoxTextChangingEventArgs参数）
{
FilteredCustomer.Clear（）;
if（searchCritiria.Text.Length> = 3）
{
SQLiteConnection dbConnection = new SQLiteConnection（" Customers.db"）;
string sSQL = null;
sSQL = @" SELECT [first]，[last]，[spouse]，[home]，[work]，[cell] FROM Customers" ;;
ISQLiteStatement dbState = dbConnection.Prepare（sSQL）;
while（dbState.Step（）== SQLiteResult.ROW）
{
string sFirst = dbState [" first" ;]作为字符串;
string sLast = dbState [" last"] as string;
string sSpouse = dbState [" spouse"] as string;
string sHome = dbState [" home"] as string;
string sWork = dbState [" work"] as string;
string sCell = dbState [" cell"] as string;
//加载到observable collection
if（searchType.SelectedIndex == 0）// name search
{
if（sFirst.Contains（searchCritiria.Text）|| sLast。包含（searchCritiria.Text）|| sSpouse.Contains（searchCritiria.Text））
FilteredCustomer.Add（新客户{第一= sFirst，最后= sLast，配偶= sSpouse，家= SHOME，工作= sWork，电池= sCell}）;
}
，否则//号码查询
{
如果（sWork.Contains（searchCritiria.Text）|| sHome.Contains（searchCritiria.Text）|| sCell.Contains（searchCritiria .Text））
FilteredCustomer.Add（新客户{first = sFirst，last = sLast，spouse = sSpouse，home = sHome，work = sWork，cell = sCell}）;
}
}
}
}
在我的程序中，我有一些类似于此的void方法。
Ex：
public void refreshItems（）
{
Items.Clear （）;
SQLiteConnection dbConnection = new SQLiteConnection（" Items.db"）;
string deleteQuery =" DELETE FROM Items WHERE name ='" +" " +"'" ;;
dbConnection.Prepare（deleteQuery）.Step（）;
string sSQL = @" SELECT * FROM Items" ;;
ISQLiteStatement dbState = dbConnection.Prepare（sSQL）;
while（dbState.Step（）== SQLiteResult.ROW）
{
string sID = dbState [" ItemID"] as string;
string sName = dbState [" name"] as string;
string sPrice = dbState [" price"] as string;
string sPosition = dbState [" category"] as string;
string sTax = dbState [" taxID"] as string;
string sMinQuantity = dbState [" minQuantity"] as string;
//加载到observable collection
Items.Add（new Item {itemID = sID，price = sPrice，name = sName，category = sPosition，minQuantity = sMinQuantity}） ;
}
}
我不知道怎么做解决这个问题。我尝试做一些研究但没有成功。任何建议将不胜感激！
解决方案
嗨MartinNowak
我看到你已经获得了解决方案（ 如何用
在UWP中进行SQlite异步？ ）。
我会在这里复制解决方案，这可以帮助其他遇到同样问题的人。
让你的方法返回
任务 而不是无效。使用void方法通常是一种不好的做法，所以这会有所帮助。因此，要将您的方法转换为等待并因此异步运行，请更改方法签名，如下所示：
< span style ="padding：0in; border：1pt windowtext; color：＃101094; font-family：inherit，serif">
private void searchCritiria_TextChanging（TextBox sender，TextBoxTextChangingEventArgs args）
{
FilteredCustomer.Clear（）;
if（searchCritiria.Text.Length> = 3）
{
SQLiteConnection dbConnection = new SQLiteConnection（" Customers.db"）;
string sSQL = null;
sSQL = @" SELECT
[first]，[last]，[spouse]，[home]，[work]，[cell] FROM Customers" ;;
ISQLiteStatement dbState = dbConnection.Prepare（sSQL）;
while（dbState.Step（）== SQLiteResult.ROW）
{
string sFirst = dbState [" first"] as string;
string sLast = dbState [" last"] as string;
string sSpouse = dbState [" spouse"] as string;
string sHome = dbState [" home"] as string;
string sWork = dbState [" work"] as string;
string sCell = dbState [" cell"] as string;
//加载到可观察的集合中
if（searchType.SelectedIndex == 0）//名称搜索
{
如果（sFirst.Contains（searchCritiria.Text）|| sLast.Contains（searchCritiria.Text）|| sSpouse.Contains（searchCritiria.Text））
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP ;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; FilteredCustomer.Add（new Customer {first = sFirst，last = sLast，spouse = sSpouse，home = sHome，work = sWork，cell = sCell}）;
}
否则//数字搜索
{
如果（sWork.Contains（searchCritiria.Text）|| sHome.Contains（searchCritiria.Text）|| sCell.Contains（searchCritiria.Text））
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP ;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; FilteredCustomer.Add（new Customer {first = sFirst，last = sLast，spouse = sSpouse，home = sHome，work = sWork，cell = sCell}）;
}
}
}
return Task.CompletedTask;
}
既然你有一个简单的方法只返回一个任务，你只需在
中调用它 async 方法 等待 例如：
<预类=" prettyprint"> 私人异步空隙searchCritiria_TextChanging（文本框发件人，TextBoxTextChangingEventArgs参数）
{ &NBSP;
等待PerformSQLTasks（）;
}
感谢您的理解。
最好的问候
Roy
I'm fairly new to databases and asynchronous programing. I'm making a POS app that will eventually have hundreds of customers and possibly thousands of transactions. When I want to do a customer search or look up a previous ticket I don't want my program to hang waiting on the results.
Here is the method that shows the search result:
private async Task searchCritiria_TextChanging(TextBox sender, TextBoxTextChangingEventArgs args)
{
FilteredCustomer.Clear();
if (searchCritiria.Text.Length >= 3)
{
SQLiteConnection dbConnection = new SQLiteConnection("Customers.db");
string sSQL = null;
sSQL = @"SELECT [first],[last],[spouse],[home],[work],[cell] FROM Customers";
ISQLiteStatement dbState = dbConnection.Prepare(sSQL);
while (dbState.Step() == SQLiteResult.ROW)
{
string sFirst = dbState["first"] as string;
string sLast = dbState["last"] as string;
string sSpouse = dbState["spouse"] as string;
string sHome = dbState["home"] as string;
string sWork = dbState["work"] as string;
string sCell = dbState["cell"] as string;
//Load into observable collection
if (searchType.SelectedIndex == 0)//name search
{
if (sFirst.Contains(searchCritiria.Text) || sLast.Contains(searchCritiria.Text) || sSpouse.Contains(searchCritiria.Text))
FilteredCustomer.Add(new Customer { first = sFirst, last = sLast, spouse = sSpouse, home = sHome, work = sWork, cell = sCell });
}
else//number search
{
if (sWork.Contains(searchCritiria.Text) || sHome.Contains(searchCritiria.Text) || sCell.Contains(searchCritiria.Text))
FilteredCustomer.Add(new Customer { first = sFirst, last = sLast, spouse = sSpouse, home = sHome, work = sWork, cell = sCell });
}
}
}
}
Throughout my program I have void methods that are structured similar to this.
Ex:
public void refreshingItems()
{
Items.Clear();
SQLiteConnection dbConnection = new SQLiteConnection("Items.db");
string deleteQuery = "DELETE FROM Items WHERE name = '" + " " + "'";
dbConnection.Prepare(deleteQuery).Step();
string sSQL = @"SELECT * FROM Items";
ISQLiteStatement dbState = dbConnection.Prepare(sSQL);
while (dbState.Step() == SQLiteResult.ROW)
{
string sID = dbState["ItemID"] as string;
string sName = dbState["name"] as string;
string sPrice = dbState["price"] as string;
string sPosition = dbState["category"] as string;
string sTax = dbState["taxID"] as string;
string sMinQuantity = dbState["minQuantity"] as string;
//Load into observable collection
Items.Add(new Item { itemID = sID, price = sPrice, name = sName, category = sPosition, minQuantity = sMinQuantity });
}
}
I'm not sure how to solve this issue. I tried doing some research but no success. Any advice would be greatly appreciated!
解决方案
Hi MartinNowak
I saw that you have got a solution in (How to make SQlite async in UWP?).
I will copy the solution in here, this could help others who are facing the same problem.
Make your method return a Task instead of void. It's generally a bad practice to use void methods eitherways so this will help. So to convert your method to be awaitable and hence run asynchronously change the method signature as below:
private void searchCritiria_TextChanging(TextBox sender, TextBoxTextChangingEventArgs args) { FilteredCustomer.Clear(); if(searchCritiria.Text.Length >= 3) { SQLiteConnection dbConnection = new SQLiteConnection("Customers.db"); string sSQL = null; sSQL = @"SELECT [first],[last],[spouse],[home],[work],[cell] FROM Customers"; ISQLiteStatement dbState = dbConnection.Prepare(sSQL); while (dbState.Step() == SQLiteResult.ROW) { string sFirst = dbState["first"] as string; string sLast = dbState["last"] as string; string sSpouse = dbState["spouse"] as string; string sHome = dbState["home"] as string; string sWork = dbState["work"] as string; string sCell = dbState["cell"] as string; //Load into observable collection if (searchType.SelectedIndex == 0)//name search { if(sFirst.Contains(searchCritiria.Text) || sLast.Contains(searchCritiria.Text) || sSpouse.Contains(searchCritiria.Text)) FilteredCustomer.Add(new Customer {first = sFirst,last = sLast,spouse = sSpouse, home = sHome, work = sWork, cell = sCell}); } else//number search { if(sWork.Contains(searchCritiria.Text)|| sHome.Contains(searchCritiria.Text) || sCell.Contains(searchCritiria.Text)) FilteredCustomer.Add(new Customer { first = sFirst, last = sLast,spouse = sSpouse, home = sHome, work = sWork, cell = sCell }); } } } return Task.CompletedTask; }
Now that you have a neat method that simply returns a task, you can simply call it in an async method with await eg:
private async void searchCritiria_TextChanging(TextBox sender, TextBoxTextChangingEventArgs args) { await PerformSQLTasks(); }Thanks for your understanding.
Best Regards
Roy
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