大约有 43,000 项符合查询结果（耗时：0.0393秒） [XML]
Pass a data.frame column name to a function
...(x[,column])
}
fun1(df, "B", max)
Alternatively, using [[ also works for selecting a single column at a time:
df <- data.frame(A=1:10, B=2:11, C=3:12)
fun1 <- function(x, column){
max(x[[column]])
}
fun1(df, "B")
...
Unable to cast object of type 'System.DBNull' to type 'System.String`
... even both. If the WHERE does not match any row, you'll get a null, if the selected row has NULL in that column, the return value is System.DBNull.
– Alexander
May 27 '14 at 7:52
...
Error message 'Unable to load one or more of the requested types. Retrieve the LoaderExceptions prop
...an also happen if your referenced DLL is "blocked". Right click on it, and select "unblock"
– Ben
Jun 10 '10 at 10:05
4
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Closing Database Connections in Java
...ent statement = connection.createStatement()) {
String sqlToExecute = "SELECT * FROM persons";
try (ResultSet resultSet = statement.execute(sqlToExecute)) {
if (resultSet.next()) {
System.out.println(resultSet.getString("name");
}
}
} catch (SQLException e) {
...
Web Application Problems (web.config errors) HTTP 500.19 with IIS7.5 and ASP.NET v2
...ou can use the Microsoft Web Platform Installer to install it. Execute it, select Products, in the left menu select Server and find URL Rewrite in the list and install it.
Or you can download it here.
share
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...
How should I cast in VB.NET?
... Dim myList AS ArrayList=new ArrayList When you write (From e In myList select CType(e.Name,String)).ToArray() it doesn't work. I came to write ... select CType(e.Name.ToString,String)).ToArray() and I retrieved my smile.
– Bellash
Mar 25 '14 at 21:13
...
can we use xpath with BeautifulSoup?
...tree.HTMLParser()
tree = etree.parse(response, htmlparser)
tree.xpath(xpathselector)
There is also a dedicated lxml.html() module with additional functionality.
Note that in the above example I passed the response object directly to lxml, as having the parser read directly from the stream is more...
How do I find an element that contains specific text in Selenium Webdriver (Python)?
... tag and if //* is categories it will not work as expected. If you need to select any specific then You can get it by declaring HTML Element tag. Like:
driver.find_element_by_xpath("//div[contains(text(),'Add User')]")
driver.find_element_by_xpath("//button[contains(text(),'Add User')]")
...
Eclipse: Java, see where class is used
Is there a way in Eclipse to select a Java class, and then bring up a list of all Java files where that class is used within a project?
...
Metadata file … could not be found error when building projects
...ound that if you right-click on your Solution in the Solution Explorer and select "Build Order" you can see the order that VS is using to rebuild your solution. It's likely out of whack.
You can correct the build order by clicking on the Dependencies tab and selecting the projects that depends on o...