DataSource Controls :: EntityDataSource Throw Exception When Update With Self-Reference?
Nov 3, 2010
For a Table A defined in the DB like this:
A :{ id, selfId, name,} where selfId is a foreign key refered to Table A itself.
I generated the Entity automatically like this:
A :{ string id; A self; string name,} when i update the entity in gridview Edit/Update CommandField
i got the exception:
Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. review the stack trace for more information about the error and where it originated in the code. Exception Details: System.NullReferenceException: Object reference not set to an instance of an object. Source Error:
[Code]....
Stack Trace:
[Code]....
I guess maybe this is caused by:
A is to be updated, and when the EntityDataSource construct the new A, the reference "self" is invalid at that moment. I do not want to modify my DB structure and do not want to lose the self reference, The event EntityDataSource_Updating is not triggered while the exception hit. so i can not access my entity at any time. Maybe the worst idea is deal the whole Update Procedure myself. However, is there any better workaround?
I have problem with Dynamic Controls in my Wizard Steps. In one of my Steps, I create a set of text boxes and checkboxes based on values from an XML document. Now, I initialise my dynamic controls using the OnInit method of the page, but at this stage there is no xml document until that step is reached, and of course I get null exception. How do I set my dynamic controls so it doesn't throw an null exception and be able to load any xml document when that step is reached?
I'm trying to throw the exception back to Page_Load but the throw statement causes error: ArgumentNullException was unhandled by user code. How can that be fixed? Also, I can't see Label1.Text displayed on the page after the ArgumentNullException occurs because the page is not re-load. If there is no exception, it's fine to not reload the page. How can I see the Label1.Text displayed?
I m having a datagrid and for client side events I m using Javascript. I have few other buttons in the same page.
when I click on datagrid and select, it is working fine. After that, if I click on any other button in the Page, It is directly going to global.asax and throwing exception.
If I click directly on other buttons, they are working fine. Once I click on Datagrid and try to click on other buttons, it is throwing that exception.
I would like to find a way to raise an exception if the Session is written to when in readonly mode. When EnableSessionState is set to "ReadOnly", values can still be put in Session, but the next request they will not be there. This seems somewhat dangerous.
One option is to create a helper class which we alway use to access session. However, this still leaves room for a developer to inadvertently use session directly, and fall into the "readonly" trap. Is there a way to create a CustomSessionStateDataStore that sits on top of the existing session code? I could not see an obvious way, and you can't inherit from System.Web.SessionState.SessionStateStoreData directly.
when my website allow user many connectionstring by text to connect database anh retrieve data. But when user define very may wrong connectionstring. So Method in DAL dataset.Fill() takes a longtime to throw exception.So mywebsite will be die.
I want to method dataset.Fill() throws exception immediately when a connectionstring wrong. How can i do that?
I'v been using SqlDataSource and ObjectDataSource for a while.I would like to know about LinqDataSource and EntityDataSource. Therefore I have 2 questions to ask.1) Why do we need to use those twos? 2) In which cirmustances (Requirements) developers are using LinqDataSource and EntityDataSource?
I have this code, and I need the "it.MembershipOption.Id" value in the "where" clause to be the <%# Eval("Id") %> from ListViewEventsOuter. I tried to add the Eval in the "where" clause but it throws an error.
What would be the best way to extend the EntityDataSource control? I have a site that implements Entity Framework and I current create my model container and add it to the HTTPCurrent context. When I create EntityDataSource controls on the page I have to go into the code behind and set the OnContextCreating to add MY context to the EntityDataSource instead of the one that EntityDataSource creates. This is because in my model I have extended the Partial Classes to support Validation and custom Save/Delete methods.I would ideally like to create a custom control that I can drop onto a page that has its context already set to the context that I created.
I have a GridView that's currently bound to an ObjectDataSource. I would like to see if it's possible to instead bind it to an EntityDataSource. However, I need to be able to apply custom filters to it.
One of the filters corresponds to a bit / boolean property in the database / EntityDataModel. It has 3 possible selections:
[Code]....
[code]....
How can I accomplish the same thing in an eSQL Where clause? There is no COALESCE function, is there an equivalent?
I have a formview with an entityDataSource. I need to include columns from related fields. I have seen many demos, with AdventureWorksDB, that imply that you can do this by using INCLUDE in the entitydatasource declaration. I have tried made many attempts and it just does not seem to work as demonstrated. I have attached the errors below and the EDS. I have also attached a JPEG of the model I am working in. Three errors demonstrating 3 different attempts to include a related table:
DataBinding: 'TmModel.tbICObjectBase' does not contain a property with the name 'Group' the code declaration for error 1: <asp:Label ID="Label1" runat="server" Text='<%# Bind("Group") %>' /> DataBinding: 'TmModel.tbICObjectBase' does not contain a property with the name 'tbICTagBase'. the code declaration for error 2: <asp:Label ID="Label1" runat="server" Text='<%# Bind("tbICTagBase.Group") %>' /> DataBinding: 'System.Data.Objects.DataClasses.EntityCollection`1[[TmModel.tbICTagBase, TmModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' does not contain a property with the name 'Group'. the code declaration for error 3: <asp:Label ID="tbICTagBasesLabel" runat="server" Text='<%# Bind("tbICTagBases.Group") %>' /> EntityDataSource <asp:EntityDataSource ID="entDSObjectBase" runat="server" AutoGenerateWhereClause="True" ConnectionString="name=IntouchDBContainer" Include="tbICTagBases" DefaultContainerName="IntouchDBContainer" EnableFlattening="False" EntitySetName="tbICObjectBases" EnableDelete="True" EnableInsert="True" EnableUpdate="True" EntityTypeFilter="tbICObjectBase"> <WhereParameters> <asp:SessionParameter SessionField="Tag" Name="RecID" Type="Int64" /> </WhereParameters> </asp:EntityDataSource>
I'm playing with an EntityDataSource and specifying a simple order by clause containing one column name, for instance "it.[DNS_NAME]".
When I run the following:
[Code]....
I get an EntitySqlException saying that @sort's type is incorrect. It is expecting a Transient.rowtype that matches one of the columns. What is going on here? Order by parameters don't really have a meaningful type other than a string in my opinion. When I try specifying DbType.String instead of TypeCode.String, the same error is thrown.
The exception:
'@sort' is not a member of type 'Transient.rowtype[(SOFTWARE_DSPL_ID,Edm.Int32(Nullable=True,DefaultValue=)),(COMPUTER_NAME,Edm.String(Nullable=True,DefaultValue=,MaxLength=64,Unicode=True,FixedLength=False)),(DNS_NAME,Edm.String(Nullable=True,DefaultValue=,MaxLength=64,Unicode=True,FixedLength=False)),(DIRECTORATE_NAME,Edm.String(Nullable=True,DefaultValue=,MaxLength=24,Unicode=True,FixedLength=False)),(OS_BROAD_CAT_NAM,Edm.String(Nullable=True,DefaultValue=,MaxLength=25,Unicode=True,FixedLength=False)),(OS,Edm.String(Nullable=True,DefaultValue=,MaxLength=64,Unicode=True,FixedLength=False)),(EQP_TYPE,Edm.String(Nullable=True,DefaultValue=,MaxLength=64,Unicode=True,FixedLength=False)),(EQP_PROP_NO,Edm.String(Nullable=True,DefaultValue=,MaxLength=10,Unicode=True,FixedLength=False))]' in the currently loaded schemas.
How can I dynamically provide the column name to order by?
Why can't I throw a custom exception from within an Exception? In code below, I get error msg "UnableToOpenDatabaseException was unhandled" even though I have catch statement for it. What am I doing wrong? and how to fix it?
I'm writing some code in which I need to use my own HttpResponse object to capture the output from a method on another object that takes an HttpResponse as a parameter. The problem is, this other object (which I cannot modify) calls HttpResponse.End(), which causes an "Object reference not set to an instance of an object" exception to be thrown. What can I do about this?
Dim myStringbuilder As New StringBuilder Dim myStringWriter As New IO.StringWriter(myStringbuilder) Dim myResponse As New Web.HttpResponse(myStringWriter)
someObject.doStuffWithHttpResponse(myResponse) ' calls myResponse.End() and crashes
Here's some more complete information about the error, thrown from the following code in a console application:
Dim myStringbuilder As New StringBuilder Dim myStringWriter As New IO.StringWriter(myStringbuilder) Dim myResponse As New Web.HttpResponse(myStringWriter) Try myResponse.End() Catch ex As Exception Console.WriteLine(ex.ToString) End Try
Here's the text of the exception:
System.NullReferenceException: Object reference not set to an instance of an object. at System.Web.HttpResponse.End() at ConsoleApplication1.Module1.Main() in C:Documents and Settingsjoe.userLocal SettingsApplication DataTemporary ProjectsConsoleApplication1Module1.vb:line 10
I use calendar extender with targetID of text box. this text box is used as a parameter in EntityDataSource. now problem is that when i select the date DataSource wasn't updated. i also try it by changing the autopostback property of textbox but after postback no changes occurs and textbox is also initialize to null
I am using an EntityDataSource with a FormView on VB.NET application. The FormView contains an AjaxControlToolKit TabContains with multiple tabs. Due to the fact that each tab is a naming container, Bind doesn't work properly for updating values (as discovered from reading other posts on stackoverflow). I instead have to declare UpdateParameters on my EntityDataSource. Example markup is as follows:
This works great, until a customer is edited and their name is set to nothing (assuming in this case, a null name is allowed). The Name UpdateParameter is set to Null but the ObjectStateEntry is not set to modified for Null properties, even if previously the Entity had a value specified. As long as the name is changed to something other than Null, everything is updated correctly.
I found a workaround by putting the following code in the Updating event of the EntityDataSource.
Dim ose As ObjectStateEntry = context.ObjectStateManager.GetObjectStateEntry(action) For Each p As Parameter In eds.UpdateParameters ose.SetModifiedProperty(p.Name) Next
This makes sure that each property in the UpdateParameters has its state set to modified. It works, but it seems like a hack and I can see it causing problems down the road. Is there anything else I could do?
I have a class that derives from System.Web.UI.Page and have set my pages to derive from this custom page class instead of Page. At runtime, the controls are never initialized and throw a NullReferenceException. I've changed some class names and namespaces in the pasted code to protect the innocent. The only thing that I currently override in my PageBase is OnPreLoad and I do call the base.OnPreLoad. I'll eventually add more functionality to this PageBase but for now all that it has is this:
[Code]....
I've tried putting this into a class library (with System.Web referenced) and I've also tried moving the class into the web application and had the same results either way. As another strange twist, I have another class with derives from PageBase called IndexPageBase and it doesn't have this problem:
