We are looking to add Microsoft Reports - SSRS to one of our internal websites.
The database has all the reporting features installed.
The website is using Entity Framework 4 for all data.
I have been able to create a report using the old fashioned way of creating a DataSet (*.XSD) and this works well.
My question though, is it possible to utilise the existing Entity Framework in the site for the data required by the reports? Rather than having to re-invent the wheel and make a whole DataSet, along with relationships etc..
It's a website and not application, so this (http://weblogs.asp.net/rajbk/archive/2010/05/09/creating-an-asp-net-report-using-visual-studio-2010-part-1.aspx) doesn't seem to apply; I don't see the DataSource (in part 2 of the tutorial)
Update
As a side-note, we would like to steer clear of expensive third-party controls etc.
Also, another way to look at the issue might be to generate the *.XSD from the entity framework entity model; is this possible? It's not ideal though would get us up and running..
Below is a quick sample of how i set the report datasource in one of my .NET winForms applications.
public void getMyReportData()
{
using (myEntityDataModel v = new myEntityDataModel())
{
var reportQuery = (from r in v.myTable
select new
{
l.ID,
l.LeaveApplicationDate,
l.EmployeeNumber,
l.EmployeeName,
l.StartDate,
l.EndDate,
l.Supervisor,
l.Department,
l.Col1,
l.Col2,
.......,
.......,
l.Address
}).ToList();
reportViewer1.LocalReport.DataSources.Clear();
ReportDataSource datasource = new ReportDataSource("nameOfReportDataset", reportQuery);
reportViewer1.LocalReport.DataSources.Add(datasource);
Stream rpt = loadEmbededReportDefinition("Report1.rdlc");
reportViewer1.LocalReport.LoadReportDefinition(rpt);
reportViewer1.RefreshReport();
//Another way of setting the reportViewer report source
string exeFolder = Path.GetDirectoryName(Application.ExecutablePath);
string reportPath = Path.Combine(exeFolder, #"rdlcReports\Report1.rdlc");
reportViewer1.LocalReport.ReportPath = reportPath;
reportParameter p = new ReportParameter("DeptID", deptID.ToString());
reportViewer1.LocalReport.SetParameters(new[] { p });
}
}
public static Stream loadEmbededReportDefinition(string reportName)
{
Assembly _assembly = Assembly.GetExecutingAssembly();
Stream _reportStream = _assembly.GetManifestResourceStream("ProjectNamespace.rdlcReportsFolder." + reportName);
return _reportStream;
}
My approach has always been to use RDLC files with object data sources and run them in 'local' mode. These data sources are ... my entities! This way, I'm using all of the same business logic, string formatting, culture awareness, etc. that I use for my web apps. There are a some quirks, but I've been able to live with them:
RDLC files don't like to live in web projects. We create a separate dummy winform project and add the RDLC files there.
I don't show reports in a viewer. I let the user download a PDF, Word, or Excel file and choose to save or open in the native viewer. This saves a bunch of headaches, but can put some folks off, depending on requirements. For mobile devices, it's pretty nice.
Since you are not using SSRS, you don't get the nice subscription feature. You are going to build that, if required. In many ways, though, I prefer this.
However, the benefits are really nice:
I'm using all of the same business logic goodness that I've already written for my views.
I have a custom ReportActionResult and DownloadReport controller method that allows me to essentially run any report via a single URL. This can be VERY handy. It sure makes a custom subscription component easier.
Report development seems to go pretty quick, now that I only need to adjust entity partial classes to tweak a little something here or there. Also - If I need to shape the data just a bit differently, I have LINQ.
We too use SSRS as "local" reports. We create Views in SQL server, then create that Object in our application along with the other EF Domain Models, and query that object using our DbContext. We use an ASPX page and use the code behind (Page_Load) to get the data passed to the report.
Here is an example of how we query it in the Page_Load Event:
var person = MyDbContext
.Query<ReportModel>()
.Where(x => x.PersonId == personId)
.Where(x => x.Year == year)
.Select(x =>
{
PersonId = x.PersonId,
Year = x.Year,
Name = x.Name
});
var datasource = new ReportDataSource("DataSet1", person.ToList());
if (!Page.IsPostBack)
{
myReport.Visible = true;
myReport.ProcessingMode = ProcessingMode.Local;
myReport.LocalReport.ReportPath = #"Areas\Person\Reports\PersonReport.rdlc";
}
myReport.LocalReport.DataSources.Clear();
myReport.LocalReport.DataSources.Add(datasource);
myReport.LocalReport.Refresh();
The trick is to create a report (.rdlc) with a blank data source connection string, a blank query block and a blank DataSetInfo (I had to modify the xml manually). They must exist in file and be blank as follows:
SomeReport.rdlc (viewing as xml)
...
<DataSources>
<DataSource Name="conx">
<ConnectionProperties>
<DataProvider />
<ConnectString />
</ConnectionProperties>
<rd:DataSourceID>19f59849-cdff-4f18-8611-3c2d78c44269</rd:DataSourceID>
</DataSource>
</DataSources>
...
<Query>
<DataSourceName>conx</DataSourceName>
<CommandText />
<rd:UseGenericDesigner>true</rd:UseGenericDesigner>
</Query>
<rd:DataSetInfo>
<rd:DataSetName>SomeDataSetName</rd:DataSetName>
</rd:DataSetInfo>
now in a page event, I use a SelectedIndexChanged on a DropDownList, bind the report datasource as follows:
protected void theDropDownList_SelectedIndexChanged(object sender, EventArgs e)
{
if (theDropDownList.SelectedIndex == 0)
return;
var ds = DataTranslator.GetRosterReport(Int64.Parse(theDropDownList.SelectedValue));
_rvReport.LocalReport.ReportPath = "SomePathToThe\\Report.rdlc";
_rvReport.LocalReport.DataSources.Add(new ReportDataSource("SomeDataSetName", ds));
_rvReport.Visible = true;
_rvReport.LocalReport.Refresh();
}
You can use a WCF-Service as Datasource and so re-use your application data and logic for your report. This requires a SQL-server standard edition at least i believe. So no can do with the free SQL-express edition.
You can use LINQ with RDLC Report which is quite easy to use
LinqNewDataContext db = new LinqNewDataContext();
var query = from c in db.tbl_Temperatures
where c.Device_Id == "Tlog1"
select c;
var datasource = new ReportDataSource("DataSet1", query.ToList());
ReportViewer1.Visible = true;
ReportViewer1.ProcessingMode = ProcessingMode.Local;
ReportViewer1.LocalReport.ReportPath = #"Report6.rdlc";
ReportViewer1.LocalReport.DataSources.Clear();
ReportViewer1.LocalReport.DataSources.Add(datasource);
ReportViewer1.LocalReport.Refresh();
Related
I have three models:
Timesheets
Employee
Manager
I am looking for all timesheets that need to be approved by a manager (many timesheets per employee, one manager per employee).
I have tried creating datasources and prefetching both Employee and Employee.Manager, but I so far no success as of yet.
Is there a trick to this? Do I need to load the query and then do another load? Or create an intermediary datasource that holds both the Timesheet and Employee data or something else?
You can do it by applying a query filter to the datasource onDataLoad event or another event. For example, you could bind the value of a dropdown with Managers to:
#datasource.query.filters.Employee.Manager._equals
- assuming that the datasource of the widget is set to Timesheets.
If you are linking to the page from another page, you could also call a script instead of using a preset action. On the link click, invoke the script below, passing it the desired manager object from the linking page.
function loadPageTimesheets(manager){
app.showPage(app.pages.Timesheets);
app.pages.Timesheets.datasource.query.filters.Employee.Manager._equals = manager;
app.pages.Timesheets.datasource.load();
}
I would recommend to redesign your app a little bit to use full power of App Maker. You can go with Directory Model (Manager -> Employees) plus one table with data (Timesheets). In this case your timesheets query can look similar to this:
// Server side script
function getTimesheets(query) {
var managerEmail = query.parameters.ManagerEmail;
var dirQuery = app.models.Directory.newQuery();
dirQuery.filters.PrimaryEmail._equals = managerEmail;
dirQuery.prefetch.DirectReports._add();
var people = dirQuery.run();
if (people.length === 0) {
return [];
}
var manager = people[0];
// Subordinates lookup can look fancier if you need recursively
// include everybody down the hierarchy chart. In this case
// it also will make sense to update prefetch above to include
// reports of reports of reports...
var subortinatesEmails = manager.DirectReports.map(function(employee) {
return employee.PrimaryEmail;
});
var tsQuery = app.models.Timesheet.newQuery();
tsQuery.filters.EmployeeEmail._in = subortinatesEmails;
return tsQuery.run();
}
this is my first post, hopefully I'm following the rules!
After a few weeks of banging my head against brick walls and endless hours of internet searches, I have decided I need to make my own post and hopefully find the answers and guidance from all you experts.
I am building an ASP.NET application (in Visual Studio 2010) which uses an SQL 2008 database and Entity Framework 4 to join the two parts together. I designed the database as a database project first, then built the Entity Model as a class project which is then referenced in the main ASP.NET project. I believe this is called Database First in Entity Framwork terms?
I'm fairly new to Web Apps (I mainly develop WinForms apps) and this is my first attempt at using Entity Framwork.
I can just about understand C# so any code samples or snippets you might supply would be preferred in VB if possible.
To give some background on where I am so far. I built a regsitration page called register.aspx and created a wizard style form using ASP:Wizard with ASP:TextBox, ASP:DropdownList and ASP:CheckBoxList it's all laid out inside a HTML table and uses CSS for some of the formatting. Once the user gets the the last page in the wizard and presses "Finish" I execute some code in the VB code behind file as follows:
Protected Sub wizardRegister_FinishButtonClick(sender As Object, e As System.Web.UI.WebControls.WizardNavigationEventArgs) Handles wizardRegister.FinishButtonClick
Dim context As New CPMModel.CPMEntities
Dim person As New CPMModel.Person
Dim employee As New CPMModel.Employee
Dim newID As Guid = Guid.NewGuid
With person
.ID = newID
.UserID = txbx_UserName.Text
.Title = ddl_Title.SelectedValue
.FirstName = txbx_FirstName.Text
.MiddleInitial = txbx_MiddleInitial.Text
.FamilyName = txbx_FamilyName.Text
.Gender = ddl_Gender.SelectedValue
.DOB = txbx_DOB.Text
.RegistrationDate = Date.Now
.RegistrationMethod = "W"
.ContactMethodID = New Guid(ddl_ContactMethodList.SelectedValue)
.UserName = txbx_UserName.Text
If Not (My.Settings.AuthenticationUsingAD) Then
.Password = txbx_Password.Text ' [todo] write call to salted password hash function
End If
.IsRedundant = False
.IsLocked = False
End With
context.AddToPeople(person)
With employee
.ID = newID
.PayrollNumber = txbx_PayrollNumber.Text
.JobTitle = txbx_JobTitle.Text
.DepartmentID = ddl_DepartmentList.SelectedValue
.OfficeNumber = txbx_OfficeNumber.Text
.HomeNumber = txbx_HomeNumber.Text
.MobileNumber = txbx_MobileNumber.Text
.BleepNumber = txbx_BleepNumber.Text
.OfficeEmail = txbx_OfficeEmail.Text
.HomeEmail = txbx_HomeEmail.Text
.IsRedundant = False
.RedundantDate = Nothing
'--------------------------
.FiledBy = Threading.Thread.CurrentPrincipal.Identity.Name
.FiledLocation = My.Computer.Name
.FiledDateTimeStamp = Date.Now
'----------------------------
End With
context.AddToEmployees(employee)
context.SaveChanges()
End Sub
The above works fine, seemed to be a sensible way of doing it (remember I'm new to Entity Framework) and gave me the results I extpected.
I have another page called manage.aspx on this page is a tab control, each tab page contains a asp:DetailsView which is bound to an asp:EntityDataSource, I have enabled Update on all the Entity Data Sources and on some I have also enabled Insert, none of the have delete enabled.
If I build and run the app at this stage everything works fine, you can press the "edit" link make changes and then press "update" and sure enough those updates are displayed on the screen instantly and the database does have the correct values in.
Here's the problem, I need to intercept the update in the above code (the bold bit) notice there is a column in my database called FiledBy, FiledLocation, and FiledDateTimeStamp. I don't want to show these columns to the user viewing the ASP.NET page but I want to update them when the user presses update (if there were any changes made). I have tried converting the ASP:DetailsView into a template and then coding the HTML side with things like;
<## Eval(User.Name) #>
I did manage to get it to put the correct values in the textboxes when in edit mode but I had the following problems;
It didn't save to the database
I have to show the textboxes which I don't want to do
I have read on several other posts on here and other websites that you can override the SaveChanges part of the Entity Framwork model one example of this is in the code below;
public override int SaveChanges()
{
var entities = ChangeTracker.Entries<YourEntityType>()
.Where(e => e.State == EntityState.Added)
.Select(e => e.Entity);
var currentDate = DateTime.Now;
foreach(var entity in entities)
{
entity.Date = currentDate;
}
return base.SaveChanges();
}
The problem is, that whilst I understand the idea, and can just about transalate it to VB I have no idea how to implement this. Where do I put the code? How do I call the code? etc.
I would ideally like to find a solution that meets the following requirements:
Doesn't get overwritten if I was to regenerate / update the Entity Model
Doesn't need to be copy and pasted for every table in my model (most but not all have the audit columns in)
Can be used for other columns, for example, if a user make a selection in a check list I may want to write some value into another (not exposed to the user) column.
Am I taking the right approach to displaying data in may webpages I certainly find the DataView and GridView limiting, I did think about creating a form like the registration form in table tags but have no Idea how to populate the textboxes etc with values from the database nor how to implement paging as many of the tables have one to many relationships, although saving changes would be easy if I did populate textboxes on a table.
Thank you all in advance to anyone who offers there support.
Kevin.
Ok so I have now got closer, but still not got it working correctly. I've used the following code to edit the value in the DetailsView on the Databound event. If writes the correct timestamp into the read only textbox but does not right this value back to the database when you press the Update button on the DetailsView control.
Protected Sub dv_Employee_DataBound(sender As Object, e As EventArgs) Handles dv_Employee.DataBound
If dv_Employee.CurrentMode = DetailsViewMode.Edit Then
For Each row In dv_Employee.Rows
If row.Cells(0).Text = "FiledDateTimeStamp" Then
row.Cells(1).Text = Date.Now()
End If
Next
End If
End Sub
I like the idea of overriding the save changes method. Your context should be a partial class, so you just need to define another class marked as partial with the same name in the same namespace and add the override to it.
Namespace CPMModel
Partial Public Class CPMEntities
...Your override here
End Class
Since this is an override of the default SaveChanges method you do not need to make any changes in how it is called. You will need to find a way to gain access to entity level properties.
Since this is the method that commits changes for all entities you will not be able to access the properties like you do in your example, since the entity class does not define an of your concrete properties. So you need to create partial classes for your entities and have them all implement an interface that defines the properties you would like to interact with.
Create interface:
Interface IDate
Property Date() as DateTime
End Interface
Create partial class for each of your entities that implements the IDate interface. (The same rules apply for these partial classes they must be marked partial, have the same name as the class they extend and live in the same namespace) Then in your SaveChanges override
public override int SaveChanges()
{
var entities = ChangeTracker.Entries<Entity>()
.Where(e => e.State == EntityState.Added)
.Select(e => e.Entity);
var currentDate = DateTime.Now;
foreach(var entity in entities)
{
***Now cast entity to type of IDate and set your value ***
entity.Date = currentDate;
}
return base.SaveChanges();
}
I don't write in Vb so I left the syntax in C#.
That should fulfill all of your requirements.
Ok, so this isn't exactly how I imagined it would work but it has infact met my needs. Kind of!
What I did was Write a Protected Sub in the code behind file of the aspx file.
Protected Sub CustomEntityUpdate_Employee(sender As Object, e As
EntityDataSourceChangingEventArgs)
Dim emp As CPMModel.Employee = e.Entity
' Check if the entity state is modified and update auditing columns
If emp.EntityState = EntityState.Modified Then
emp.FiledDateTimeStamp = Date.Now()
emp.FiledBy = Threading.Thread.CurrentPrincipal.Identity.Name
emp.FiledLocation = My.Computer.Name
End If
End Sub
Then in the aspx page I edited the Entity datasource code to call the above sub routine
#nUpdating="CustomEntityUpdate_Employee"
<asp:EntityDataSource
ID="eds_Employee"
runat="server"
ConnectionString="name=CPMEntities"
DefaultContainerName="CPMEntities"
EnableFlattening="False"
EnableUpdate="True"
EntitySetName="Employees"
AutoGenerateWhereClause="True"
Where=""
EntityTypeFilter="Employee"
**OnUpdating="CustomEntityUpdate_Employee">**
<WhereParameters>
<asp:SessionParameter
Name="ID"
SessionField="UserID" />
</WhereParameters>
</asp:EntityDataSource>
The Protected Sub, checks if the entity has been modified and if it has updates the entity auditing columns with the values I wanted.
It works but it will certainly make for a lot more code, I ideally would like a way to package this up perhaps into a class and just call the sub from the various aspx pages via the OnUpdating event and have the class figure out which entity was making the call and handle all the logic there.
I have a lot of XSL files in my ASP.NET web app. A lot. I generate a bunch of AJAX HTML responses using this kind of generic transform method:
public void Transform(XmlDocument xml, string xslPath)
{
...
XslTransform myXslTrans = new XslTransform();
myXslTrans.Load(xslPath);
myXslTrans.Transform(xml,null, HttpContext.Current.Response.Output);
}
I'd like to move the XSL definitions into SQL Server, using a column of type xml.
I would store an entire XSL file in a single row in SQL, and each XSL is self-contained (no imports). I would read out the XSL definition from SQL into my XslTransform object.
Something like this:
public void Transform(XmlDocument xml, string xslKey)
{
...
SqlCommand cmd = new SqlCommand("GetXslDefinition");
cmd.AddParameter("#xslKey", SqlDbType.VarChar).Value = xslKey;
// where the result set has a single column of XSL: "<xslt:stylesheet>..."
...
SqlDataReader dr = cmd.ExecuteReader();
if(dr.Read()) {
SqlXml xsl = dr.GetSqlXml(0);
XslTransform myXslTrans = new XslTransform();
myXslTrans.Load(xsl.CreateReader());
myXslTrans.Transform(xml,null, HttpContext.Current.Response.Output);
}
}
It seems like a straightforward way to:
add metadata to each XSL, like lastUsed, useCount, etc.
bulk update/search capabilities
prevent lots of disk access
avoid referencing relative paths and organizing files
allow XSL changes without redeploying (I could even write an admin page that selects/updates the XSL in the database)
Has anyone tried this before? Are there any caveats?
EDIT
Caveats that responders have listed:
disk access isn't guaranteed to diminish
this will break xsl:includes
The two big issues I can see are:
We use a lot of includes to ensure that we only do things once, storing the XSLT in the database would stop us from doing that.
It makes updating XSLs more interesting - we've been quite happy to dump new .xsl files into deployed sites without doing a full update of the site. For that matter we've got bits of code that look for client specific xsl in a folder and those bits of code can reach back up to common code (templates) in the root - so I'm not sure about the redeploy thing at all, but this will depend very much on the particular use case, yours is certainly different to ours.
In terms of disk access, hmm... the db still has to go access the disk to pull the data and if you're talking about caching then the db isn't a requirement for enabling caching.
Have to agree about the update/search options - you can do stuff with Powershell but that needs to be run on the server and that's not always a good idea.
Technically I can see no reason why not (excepting the wish to do includes as above) but practically it seems to be fairly balanced with good arguments either way.
I store XSLTs in a database in my application dbscript. (However I keep them in an NVARCHAR column, since it also runs on SQL Server 2000)
Since users are able to edit their XSLTs, I needed to write a custom validator which loads the text of TextBox in a .Net XslCompiledTransform object like this:
args.IsValid = true;
if (args.Value.Trim() == "")
return;
try
{
System.IO.TextReader rd = new System.IO.StringReader(args.Value);
System.Xml.XmlReader xrd = System.Xml.XmlReader.Create(rd);
System.Xml.Xsl.XslCompiledTransform xslt = new System.Xml.Xsl.XslCompiledTransform();
System.Xml.Xsl.XsltSettings xslts = new System.Xml.Xsl.XsltSettings(false, false);
xslt.Load(xrd, xslts, new System.Xml.XmlUrlResolver());
xrd.Close();
}
catch (Exception ex)
{
this.ErrorMessage = (string.IsNullOrEmpty(sErrorMessage) ? "" : (sErrorMessage + "<br/>") +
ex.Message);
if (ex.InnerException != null)
{
ex = ex.InnerException;
this.ErrorMessage += "<br />" + ex.Message;
}
args.IsValid = false;
}
As for your points:
file I/O will be replaced by database-generated disk I/O, so no gains there
deployment changes to providing an INSERT/UPDATE script containing the new data
i've found how to bind an asp:Menu to XML. i've found how to bind an asp:Menu to a site map (which is really binding it to XML). How do you bind an asp:Menu to a database?
The .NET Framework provides multiple data sources:
HierarchicalDataSourceControl
XmlDataSource
SiteMapDataSource
DataSourceControl
SqlDataSource
AccessDataSource
LinqDataSource
i want to use one that represents data from an SQL Server table. The data is stored in the standard hierarchical format that everyone uses:
NodeID ParentNodeID Caption Url
======== ============== ========= =================
{3234... {3632... stackoverflow http://stackov...
{3632... (null) Questions ~/questions.aspx
{3233... (null) Tags ~/tags.aspx
{3235... {3632... google http://www.goo...
And the query to return all the rows would be:
SELECT * FROM Nodes
What is the secret method that Microsoft intended me to use to mash that data into an asp:Menu?
Update: There is a good article on aspalliance.com: Building a Database Driven Hierarchical Menu using ASP.NET 2.0. Unfortunatly it describes how to perform XML data binding; while i'm interested in database binding.
There is a good article on aspalliance.com: Building a Database Driven Hierarchical Menu using ASP.NET 2.0. Each step is explained and nicely illustrated.
"In this article, Michael demonstrates how to create a database driven hierarchical menu with only a few lines of code using ASP.NET 2.0. This is a must read tutorial for everyone who needs a professional menu that is powerful and flexible with simplistic design."
The code for could be:
protected void LoadData()
{
DataSet ds = new DataSet();
string connStr = YOUR_CONNECTION_STRING_HERE;
using(SqlConnection conn = newSqlConnection(connStr))
{
string sql = "Select NodeID, Caption, Url, ParentID from Menu";
SqlDataAdapter da = newSqlDataAdapter(sql, conn);
da.Fill(ds);
da.Dispose();
}
ds.DataSetName = "Menus";
ds.Tables[0].TableName = "Menu";
DataRelation relation = newDataRelation("ParentChild",
ds.Tables["Menu"].Columns["NodeID"],
ds.Tables["Menu"].Columns["ParentID"], true);
relation.Nested = true;
ds.Relations.Add(relation);
xmlDataSource.Data = ds.GetXml();
}
The menu does not support binding to SqlDataSource because it is a HierarchicalDataBoundControl - only hierarchical datasources are supported. You should implement your own HierarchicalDataSourceControl. Check here for an example. Alternatively you could create a custom sitemap provider and use the SiteMapDataSource as demonstrated here. Finally you can use a 3'rd party control which can bind to SqlDataSource.
Part of the web application I'm working on is an area displaying messages from management to 1...n users. I have a DataAccess project that contains the LINQ to SQL classes, and a website project that is the UI. My database looks like this:
User -> MessageDetail <- Message <- MessageCategory
MessageDetail is a join table that also contains an IsRead flag.
The list of messages is grouped by category. I have two nested ListView controls on the page -- One outputs the group name, while a second one nested inside that is bound to MessageDetails and outputs the messages themselves. In the code-behind for the page listing the messages I have the following code:
protected void MessageListDataSource_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
var db = new DataContext();
// parse the input strings from the web form
int categoryIDFilter;
DateTime dateFilter;
string catFilterString = MessagesCategoryFilter.SelectedValue;
string dateFilterString = MessagesDateFilter.SelectedValue;
// TryParse will return default values if parsing is unsuccessful (i.e. if "all" is selected"):
// DateTime.MinValue for dates, 0 for int
DateTime.TryParse(dateFilterString, out dateFilter);
Int32.TryParse(catFilterString, out categoryIDFilter);
bool showRead = MessagesReadFilter.Checked;
var messages =
from detail in db.MessageDetails
where detail.UserID == (int)Session["UserID"]
where detail.Message.IsPublished
where detail.Message.MessageCategoryID == categoryIDFilter || (categoryIDFilter == 0)
where dateFilter == detail.Message.PublishDate.Value.Date || (dateFilter == DateTime.MinValue)
// is unread, showRead filter is on, or message was marked read today
where detail.IsRead == false || showRead || detail.ReadDate.Value.Date == DateTime.Today
orderby detail.Message.PublishDate descending
group detail by detail.Message.MessageCategory into categories
orderby categories.Key.Name
select new
{
MessageCategory = categories.Key,
MessageDetails = categories.Select(d => d)
};
e.Result = messages;
}
This code works, but sticking a huge LINQ statement like this in the code-behind for a LinqDataSource control just doesn't sit right with me.
It seems like I'm still coding queries into the user interface, only now it's LINQ instead of SQL. However, I feel that building another layer between the L2S classes and the UI would cut back on some of the flexibility of LINQ. Isn't the whole point to reduce the amount of code you write to fetch data?
Is there some possible middle ground I'm not seeing, or am I just misunderstanding the way LINQ to SQL is supposed to be used? Advice would be greatly appreciated.
All your LINQ querys should be in a business logic class, no change from older methodologies like ADO.
If you are a purist you should always return List(of T) from your methods in the business class, in fact, the datacontext should only be visible to the business classes.
Then you can manipulate the list in the user interface.
If you are a pragmatist, you can return a IQueryable object and make some manipulations in the user interface.
Regardless of LINQ, I think that mixing presentation code with database-relaed code is not a good idea. I would create a simple DB abstraction layer on top of LINQ queries. In my opinion LINQ is just a convenient tool, that doesn't have a serious impact on traditional application design.