WebMatrix :: Check For Null / Empty Strings On Dynamic Objects?
Aug 20, 2010
What is the proper way to check for null or empty strings on dynamic objects? This is the only solution I've found so far:
if (admin.PasswordHash.GetType() == typeof(DBNull) || admin.PasswordHash == string.Empty)
If the field is null, the object returned is DBNull.Value, but if the field is empty string, it's return as a System.String object. This makes it impossible to do regular "admin.PasswordHash == DBNull.Value" check, as that will fail whenever the field has been set to empty string. Is my example the right (and only) way to go?
we have a AutoGenerateColumns-enabled WmxDataGrid in which we are able to update table rows in a DataBase connected with a SqlDataSource.
Each time we clear a field an empty string is written to the database where we want to write DBNull values.
At the moment we generate the update string via UPDATE... SET.. and the SQL Server function NULLIF(value, '').
Works proper but when I want to add the values to e.NewValues in BeginUpdate event I'm not able to read the values from the auto generated text boxes. How do I do that? Is there an easier way to automatically convert empty strings to NULL values?
I have set the value of an int parameter to the attribute of a textbox.The textbox can be empty or null, how to check whether the parameter is empty or null?
How do I check if my value is empty AND Isnull? I need to check for both, using ISNULL is not enough because the data can change just so that it is empty.
I'm fetching som data from AD and I notice that I'm getting an exeption and notice that one of the users field that I'm fetching is empty, how can I prevent exeption.
this is my sql query and its work fine in my code but it only check ParentDeptID IS NULL it not working when ParentDeptID field is empty how can i check it
("select DeptID,DeptName,(select count(*) FROM HrDept " _ & "WHERE ParentDeptID=sc.DeptID) childnodecount FROM HrDept sc where ParentDeptID IS NULL ", _ objConn)
Using MVC 2 and VS 2010 RC.I have a varchar database column set to NOT NULL and I use the Entity Framework to bind the column to a textbox. I want a user to be able to leave the textbox blank and have an empty string inserted into the database column. However, MVC is trying to set the property to null during the Create postback, which causes ModelState.IsValid to be false and subsequently the validation UI is triggered with the message "The value '' is invalid".Here is the model:
[Code]....
The controller:
[AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(Candidate c ) { if (ModelState.IsValid) // This is false when the textbox is left blank.
In this test application, I am filtering by two ControlParameters. As you can see in the first codeblock, both parameters have a default value of %. This code works great. However, in the second code block, please note that the Default Values are eliminated. The second code block works as long as neither Textbox's text is blank. For some reason, when .NET evaluates the filter expression and inserts "" into the expression, it seems to bug out and case none of my results to be filtered.
I am able to verify this behavior by setting the defaultvalue="" for each ControlParameter.Obviously I have found a workaround, but I would like to know why the FilterExpression breaks down when an empty string is provided.
Code Block 1:
<asp:SqlDataSource ID="Customer_Data" runat="server" ConnectionString='<%$ ConnectionStrings:connectionString %>' SelectCommand="SELECT Station, StoreFront, CustomerID as CustID FROM vStations" [code]...
I have setup my business object to have a create_date and edit_date members both datetime datatypes. My company want to display the create_date and edit_date fields in a gridview for each transaction. The problem i have is that after insterting a record it will have a valid create_date but no edit_date and when displayed in the gridview it defaults to datetime.minvalue (My default). How on earth do i show an empty field in my gridview for a null datetime field in the database?
I am using similar architecture to the Imar Spaanjaars example of a tiered solution. With a few small tweeks it has worked well for me for ages. I am passing a List<Database> to my object datasource which connects to my gridview.
I'm trying to write a regular expression that allows positive & negative floating point numbers, but doesn't allow empty strings and characters.I have managed to create this
[Code]....
but it allows empty strings and I can't figure out how to add [+-].
My program is a web app which asks the user to input a temperature.
I have a little web app derived from one template (LinkDirectory). It works fine both on local and on live website.
But, when I download the database (which is filled with valud data, visible in the web app) from the website data (for maintenance purposes), it appear empty (no tables) in my local wite.
What did I miss ? is there a better way to get the database back home ?
based on the code below how can I tell if the recordset returned is empty and if the grid is emptyIf data is empty how can I tell data.Count(); and data.RecordCount(); generate errorsHow can I tell if the grid is empty, has no rows or if the rowcount = 0
var db = Database.Open("StarterSite"); var sqlQ = "SELECT * FROM table1 ORDER BY Name"; var data = db.Query(sqlQ); var grid1 = new webgrid(data); grid1.gethtml();
I'm working on a project in which we have a database, data layer (entity framework), business layer and web/UI layer.I want to use ASP.NET Dynamic Data for the web layer, but don't want it to access the data layer or database, as I want it to be purely running off business logic, and not directly accessing the data.However, it appears that Dynamic Data only allows Linq-to-SQL or entity framework data sources to be used.Has anyone used it with business-layer objects instead?
i am using a search box for my application which returns a dataset. however when i click on the search button it returns an empty table result. how could i add validation so it doesnt accept empty strings or numbers.
I'm used to using VB.net for web programming.Often, I have something like:
Dim s as string = Session("s")
I get a string value for s from the web session. If there is no value in the web session, I get a blank string.However, AFAIK, in C#, I have to have something like the code below to do the same thing.
string s; try { s = Session["s"].ToString(); } catch { s = ""; }
I use asp:Login control, user can login properly, but while checking user Profile information within LoggedIn event of Login control, all of the fields in the Profile objects are empty. Also, User.Identity.IsAuthenticated always returns false. But, all of these issue solved while navigating to another page. Why User.Identity.IsAuthenticated returns false, even user logged-in properly? And, is there any way to get user's profile information within LoggedIn event of Login control?
I have a WCF service with cyclic references that I was using the CyclicReferencesAwareAttribute attribute (http://chabster.blogspot.com/2008/02/wcf-cyclic-references-support.html) to solve. However now I want to use the same service with a Silverlight client. Receiving data works well on the Silverlight client with this method, however the CyclicReferencesAwareAttribute attribute does not work on the Silverlight side when I want to send objects back again.
I have changed to use the IsReference property on the data contract which is supposed to get round with this issue. However now the objects that are returned are empty! (All fields are either default or null). This is the same in my ASP.NET client (original) and my Silverlight client.
Has anyone hit is issue before? Here is the attribute [System.Runtime.Serialization.DataContract(Namespace="http://testnamespace.co.uk/entities", IsReference=true)]
Now I know this works.. but what is the right way to have this? I don't want to be checking something twice instead of just having it written out once.
when we select a check boxes creat dynamic check boxes. I have a main catagory check box when we select this main catagory check box creat subcatagory check boxes related to main catagory dynamically.
