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问题 I'd like to know how to validate my 4 edittext fields if one or more of these fields are left empty after tapping the button to process the inputs. I have searched many solutions like using toast but It think it's not appropriate for multiple edittext fields and using textwatchers. I'd like the app to show a pop-up message or alert dialog box saying "Please fill up the necessary fields." Any help would be appreciated. 回答1: You can use below common function for checking the Null values of the

问题 I'm using dynamic Linq to order a result set depending on which column is passed in. I'm using this to order a table when a user clicks on a table column. If the property im ordering on is a class which is null the code falls over, i want to be able to dynamically orderby a string but cater for nulls if the property is a class. This is the code from the System.Linq.Dynamic class im using. public static IQueryable OrderBy(this IQueryable source, string ordering, params object[] values) { if

问题 Is it possible in T-SQL to write a proper query reflecting this pseudo-code: SELECT {primary_key}, {column_name} FROM {table} WHERE {any column_name value} is NULL i.e. without referencing each column-name explicitly. Sounds simple enough but I've searched pretty extensively and found nothing. 回答1: You have to use dynamic sql to solve that problem. I have demonstrated how it could be done. With this sql you can pick a table and check the row with id = 1 for columns being null and primary keys

问题 I want to do a simple Rails.cache.fetch and expire it after about 10 minutes. The cache gets filled with json data from an external API. However the external API is not reachable sometimes. So when the cache expires and tries to fetch new json data, the cache content gets invalid. How can I make Rails.cache.fetch ONLY EXPIRE the cache if the fetch_json returns valid data? However the cache should expire after 10 minutes if it receives new valid data. This is how I tried to do it, but it does

问题 I'm newbie in JavaScript, i hope you can help me, as in topic, null property. var add = document.getElementById('addition').checked; var subs = document.getElementById('substraction').checked; var multi = document.getElementById('multiplication').checked; var div = document.getElementById('division').checked; var result = 0; var x = parseInt(document.getElementById('firstNumber').value); var y = parseInt(document.getElementById('secondNumber').value); function calculator() { if (add) { result

问题 I have an MVC app via SharpArch. In the view I have: Html.DropDownListFor(x => x.Location, new SelectList(Model.PossibleLocations, "Id", "Address"), "-- No Location --") I have 2 issues. The Dropdown is not getting updated when the view gets bound to the model. A selection gets persisted correctly except when I try the top "no location". I was able to take care of the first point by changing x.Location to x.Location.Id but then I had other issues. I can find plenty of examples for

问题 I have a dataframe with a column of arraytype that can contain integer values. If no values it will contain only one and it will be the null value Important : note the column will not be null but an array with a single value; null > val df: DataFrame = Seq(("foo", Seq(Some(2), Some(3))), ("bar", Seq(None))).toDF("k", "v") df: org.apache.spark.sql.DataFrame = [k: string, v: array<int>] > df.show() +---+------+ | k| v| +---+------+ |foo|[2, 3]| |bar|[null]| Question : I'd like to get the rows

问题 I am developing an application with swift 3.0. Where what I want to do is, from the "MainMapVC" class, which is the view where you have a map with a date slider (see the attached image). I want to move the slider and send that slider position (1,2 or 3) to LeftSideViewController which is the side view (the legend) updating the content depending on the selected date. View of MainMapVC: View of MainMapVC with Legend: Well, and I've come to the point where I have to pass a value between the two

问题 I have the following code which was ok until someone else put some other code in the site which sorta mucks it up now. This is my code: var existingContext = HttpContext.Current; var writer = new StringWriter(); var response = new HttpResponse(writer); var context = new HttpContext(existingContext.Request, response) { User = existingContext.User }; HttpContext.Current = context; HttpContext.Current.SetSessionStateBehavior(System.Web.SessionState.SessionStateBehavior.Default); HttpContext

问题 We would like to implement a simple rule in which NHibernate would assign (persist) NULL to the database when the ID for the entity is equal to -1. For example, we have an "in system" account which should be persisted to the database as NULL. If we try to persist the ID of -1 to the database we get a Foreign key exception because the ID does not exist in the foreign table. We are using NHibernate with FluentNhibernate. 回答1: I think you didn't a proper mapping of your entity. If it were