PowerApps -如果Lookup（）为外部数据源为零 - 电源应用程序中断
我有一个PowerBi报告，上面有几个数据源，SQL查询和Excel连接器。
有关我们产品的SQL数据数据，而Excel是销售人员关于上述产品的活着数据。
PowerBi具有PowerApp可视化。 Power应用程序有3页：
第1页是登陆页面，画廊从PowerBi
Page 2显示数据是一个表单编辑页面，可以在Excel电子表格中编辑注释，我们知道存在因为我们在PowerBi报告中看到了这些注释
第3页是一个表单编辑页面，在Excel电子表格中添加新笔记，我们知道我们必须添加，因为我们在PBI报告中没有看到它们
<<强>第1页是两个按钮，“编辑”和“新”，可导航到适当的页面。
现在，WTF时刻
如果 有笔记，用户单击 new 按钮，然后PowerApps将行添加到Excel电子表格中，引起重复，因此PowerBi报告无法刷新。它破裂了。
如果该产品没有注释，则用户单击 eding 按钮，然后PowerApps进行lookup（ExcelsPreadsheet，column = Gallery1.Selected.selected.selected.powerbivalue导致 null 值，因此不支持可怕的服务器响应：表达“ ... eq null”。
如果我尝试添加“ Isempty（）”以进行先发制化，首先运行'lookup（）'' ”和“ Iserror”。
，“ Isblankorerror 在其他人遇到的问题中，您甚至无法使用错误处理程序“ Iserror（）” 。
em>因为它最终会产生 null 结果，所以Power Apps breaks
我如何从数据源读取空值？
I have a PowerBi report with several data sources, SQL query and Excel connector.
The SQL data data on our Products whereas the Excel is living data on salesperson notes on said products.
The PowerBI has a PowerApp visualization. The Power App has 3 pages:
Page 1 is landing page that Gallery displays data from PowerBi
Page 2 is a form edit page to edit notes in the Excel spreadsheet that we know exists because we saw those notes in the PowerBi report
Page 3 is a form edit page to add new notes in the Excel spreadsheet that we know we have to add because we did not see them in the PBI report
On Page 1 are two buttons, "Edit" and "New" that navigates to the proper page.
Now here the WTF moment
IF the Product has notes and the user clicks on the NEW button, then PowerApps adds the line to the Excel spreadsheet, causing duplicates and thus the PowerBi report cannot refresh. It breaks.
If the Product does not have notes and the user clicks on the EDIT button then PowerApps does a LookUp(ExcelSpreadsheet, Column=Gallery1.Selected.PowerBiValue which results in a NULL value and thus breaks with a dreaded server response: expression "... eq null" is not supported.
If I try to add the 'IsEmpty()' to preemptive counter it, the 'Lookup()' is run first thus breaking before it gets to the 'IsEmpty()', same goes with 'IsBlank', 'IsBlankOrError', and 'IsError'.
I have Googled the living %(#$* out of this and there seems to be nothing on it, as this is in direct relation to 'LookUp' on the Excel Spreadsheet not a dropdown or in app text box that other people have issues with. How is it that you can't even use the error handler 'IsError()' as it breaks before the handler can even have a chance to do anything.
If I use LookUp(ExcelSpreadsheet, Column=Gallery1.Selected.PowerBiValue) in any way, shape, or form, with or without If clauses, because it will eventually produce a NULL result, Power Apps breaks
How do I read null values from a data source?
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解决方案：
由于PowerBi报告中还在“ Living Data” Excel电子表格中，因此我拥有PowerBi send 将生活数据值以及SQL查询产品值与PowerApp的查询。由于NULL现在是从PowerBi发送的，而不是从PowerApps中的Excel查询，因此我可以拥有1个按钮，onselect属性读取：
SOLUTION:
Since the "living data" Excel spreadsheet is also in the PowerBi report, I have PowerBi send the living data values along with the SQL queried product values to the PowerApp. Since the NULL is now a sent from PowerBi instead of queried from Excel within PowerApps, I can have 1 button that's OnSelect property reads: