I want to use multiple order by in my query, and i am using LINQ.i am new to LINQ, i have tried the examples given on stackoverflow. but i dont know why these are not working for me , i am sure i am wrong some where. below is my situation.
I got a project in which created using LINQ. I have little task to set order of column. Actually what is my task there is a column created date by which its ordering now. Now i want to use Createddate as well a sortOrder column for ordering.Below is code used for it:
Code in page load method
ViewState["SortDirection"] = "desc";
ViewState["SortColumn"] = "createddate";
BindAllTopics(ViewState["SortDirection"].ToString(), ViewState["SortColumn"].ToString());
And my BindAllTopic Method is as bellow:
protected void BindAllTopics(string SortType, string SortColumn)
{
var LstTopics = (from topic in Dbobj.T_topic select topic).ToList();
if (LstTopics.Count() > 0)
{
if (SortType == "ASC")
{
LstTopics = LstTopics.OrderBy(q => q.Name).ToList();
}
else
{
LstTopics = LstTopics.OrderByDescending(q => q.Name).ThenBy(q => q.SortOrder).ToList();
}
GrdTopics.DataSource = LstTopics.ToList();
GrdTopics.PageSize = 25;
GrdTopics.DataBind();
}
else
{
GrdTopics.DataSource = null;
GrdTopics.DataBind();
lblMsg.DisplayMessage(StatusMessages.InfoMessage, "No Topics Found.");
}
}
I want to sort it firstly by sortorder which is of int type and then by Createddate.
Please help me..
you can add one more ThenBy() in trail
LstTopics.OrderByDescending(q => q.Name).ThenBy(q => q.SortOrder).ThenBy(m=>m.date)
If you do not want to use Dynamic Linq the following see Marc Gravell's answer below
stackoverflow:Dynamic Linq OrderBy
After correction you can achieve this by Dynamic Linq
LstTopics = LstTopics.OrderBy(SortColumn + " " + SortType);)
Related
I receive the following error when I try to run my code. I haven't managed to solve it yet, please Help:
edit: Marked with * where it fails.
>
public IQueryable<Video> GetVideos([QueryString("id")] int? categorieId)
{
var _db = new TeleviziuneAcademicaAspSilverlight.Models.VideoContext();
IQueryable<Video> query = *_db.Videos;*
if (categorieId.HasValue && categorieId > 0)
{
query = query.Where(v => v.CategorieID == categorieId);
}
return query;
Change
IQueryable<Video> query =
to
IQueryable<Appname.Models.Video> query =
The reason for your error is that you have the type Video defined twice and because of using a short type name you accidentally reference not the one Video you should.
Also change it in the method's return value
public IQueryable<Appname.Models.Video> GetVideos( ... )
You seem to have two classes called Video. If you need both, you'll need to project from one to the other before your return statement:
return query.Select(dbVideo => new Appname.Video()
{
Prop1 = dbVideo.Prop1,
Prop2 = dbVideo.Prop2,
// etc.
});
Though you'll probably need to change the return type to an IEnumerable<> if you do that.
If you can just work with Appname.Models.Video, change IQueryable<Video> to IQueryable<Appname.Models.Video> in the method signature and the method body.
Morning,
I would like to know how to write the following SQL statement in LINQ.
SELECT TOP 6 * FROM Questions
ORDER BY NEWID()
I would also like to know, how i could bind this to a asp.net repeater control to display the 6 questions.
Many thanks :)
The Linq style would be
Questions.OrderBy(q=>Guid.NewGuid()).Take(6)
then you attach that to a repeater by setting its DataSource property to the above, and calling the DataBind method.
You would have to be able to invoke the NEWID() function to generate your random guids. To do so, you could take some hints here and first create a pseudo-method mapped to the NEWID() function on your data context.
[System.Data.Linq.Mapping.Function(Name="NEWID", IsComposable=true)]
public Guid NewId()
{
throw new NotImplementedException();
}
Once that is set, you could then write your query to use this function:
var query = dc.Questions
.OrderBy(question => dc.NewId())
.Take(6);
You can inspect the SQL query generated for this and it should match.
Questions.OrderBy(q=>Sql.NewGuid()).Take(6)
This will invoke the NEWID() in SQL statement.
(from db in context.Questions
order by Guid.NewGuid()
select db).Take(6);
I know answer is already selected, but still I'm adding my way to achieve this. Faced same situation today and tried couple of ways, used questions.OrderBy(q => Guid.NewGuid()).ToList() and couple of more suggestions. Later I thought to add a new field string RandomOrder in view model and assigned Guid.NewGuid().ToString() in loop and then used questions.OrderBy(i => i.RandomOrder).ToList() and this worked great.
I had requirement to shuffle questions if author selected option shuffleAlways while creating assessment. If not then sort on regular sorting order. Here is complete solution:
private List<AssessmentQuestionsViewModel> LoadAllQuestions(string assessmentId, bool shuffleQuestions)
{
List<AssessmentQuestionsViewModel> questions = new List<AssessmentQuestionsViewModel>();
var items = assessmentQuestionRepository.GetAll().Where(i => i.AssessmentId == assessmentId).ToList();
foreach (var item in items)
{
questions.Add(new AssessmentQuestionsViewModel
{
Id = item.Id,
AssessmentId = item.AssessmentId,
QuestionText = item.QuestionText,
HintText = item.HintText,
QuestionType = item.QuestionType,
MaxMarks = item.MaxMarks,
SortOrder = item.SortOrder,
RandomOrder = Guid.NewGuid().ToString(),
Answers = LoadAllAnswers(item.Id)
});
}
if (shuffleQuestions)
{
questions = questions.OrderBy(i => i.RandomOrder).ToList();
}
else
{
questions = questions.OrderBy(i => i.SortOrder).ToList();
}
return questions;
}
And this worked like charm. Hope this help others.
I assume you are using ORDER BY NEWID() as a way to select random data from your questions? If so, you should avoid using NEWID() (or it's LINQ equivalent), causes tons a new guid to be generated for every record in your table. On a large dataset, that's devestating.
Instead, see Linq Orderby random ThreadSafe for use in ASP.NET for an optimized solution to random sorts. Then just add a take operator and your set.
Random random = new Random();
int seed = random.Next();
var RandomQuestions = Questions.OrderBy( s => (~(s.Shuffle & seed)) & (s.Shuffle | seed)); // ^ seed);
return RandomQuestions.Take(6);
Is it possible to programatically sort properties on DocumentType? I am creating them from code, but not sure how to order them.
Any suggestions much appreciated.
It depends on how and what you want to sort, but here's an example of how you might sort them:
DocumentType dt = DocumentType.GetByAlias("umbTextpage");
//Get the one you want to move to the top.
var property = dt.PropertyTypes.First(p => p.Alias == "bodyText");
//Get the rest. Make sure you have the right TabId.
var otherProperties = dt.PropertyTypes.Where(p => p.Alias != "bodyText" && p.TabId == 8).ToList();
property.SortOrder = 0;
property.Save();
int i = 1;
foreach (var p in otherProperties)
{
p.SortOrder = i++;
p.Save();
}
Hopefully, that gives you some sort of starting place, if you haven't already figured it our already... The easiest way to get the TabId is to look at the cmsTab table in the database.
Do you refer sorting based of the sub-pages of particular node? I mean your question little confuse...
anyway if you want to sort sub-pages; you can do that by something like following.
var eventsNode = #Model.NodeById(1058).orderbydesending("createddate");
Thanks,
Developerjigar
Linq to entity query to delete a specific column from a table by matching a condition`
public ActionResult deleteChecks(string checkValue)
{
check_master checks = (from table in db.check_master
where table.check_code == checkValue
select table).First();
//now how to delete/remove checks.mcheck
return View("Edit");
}`
Only want to update a single column element with null value(of selected row) from the table check_master
You can set a single property (which maps to a column) to null and save it to the database
foreach(check_master check in checks)
{
check.mcheck = null;
}
db.SaveChanges();
using (NorthwindDataContext db = new NorthwindDataContext())
{
// Retrieve the existing entity. Database Call 1
Product product = db.Products.First(p => p.ProductID == 1);
// Change the properties. LINQ to SQL knows
// these specific properties have changed.
product.UnitsInStock = 14;
// Flush the changes. Database Call 2
db.SubmitChanges();
}
Entity framework works with constant table scheme only.
Tell please, what your global aim is, may be there's some more suitable way to do it.
Updated:
foreach(var chm in db.check_master)
{
chm.mcheck = null;
}
db.SaveChanges();
I believe that Linq to Entities only support DML, it does not support DDL operations.
So you would have to use stored procedure or ADO.NET raw query.
EDIT
you can do simple update like this :
public ActionResult deleteChecks(string checkValue)
{
check_master checks = (from table in db.check_master
where table.check_code == checkValue
select table).First();
checks.mcheck = null;
db.SaveChanges();
return View("Edit");
}`
I'm modifying the "Edit.aspx" default page template used by ASP.NET Dynamic Data and adding some additional controls. I know that I can find the type of object being edited by looking at DetailsDataSource.GetTable().EntityType, but how can I see the actual object itself? Also, can I change the properties of the object and tell the data context to submit those changes?
Maybe you have found a solution already, however I'd like to share my expresience on this.
It turned out to be a great pita, but I've managed to obtain the editing row. I had to extract the DetailsDataSource WhereParameters and then create a query in runtime.
The code below works for tables with a single primary key. If you have compound keys, I guess, it will require modifications:
Parameter param = null;
foreach(object item in (DetailsDataSource.WhereParameters[0] as DynamicQueryStringParameter).GetWhereParameters(DetailsDataSource)) {
param = (Parameter)item;
break;
}
IQueryable query = DetailsDataSource.GetTable().GetQuery();
ParameterExpression lambdaArgument = Expression.Parameter(query.ElementType, "");
object paramValue = Convert.ChangeType(param.DefaultValue, param.Type);
Expression compareExpr = Expression.Equal(
Expression.Property(lambdaArgument, param.Name),
Expression.Constant(paramValue)
);
Expression lambda = Expression.Lambda(compareExpr, lambdaArgument);
Expression filteredQuery = Expression.Call(typeof(Queryable), "Where", new Type[] { query.ElementType }, query.Expression, lambda);
var WANTED = query.Provider.CreateQuery(filteredQuery).Cast<object>().FirstOrDefault<object>();
If it's a DD object you may be able to use FieldTemplateUserControl.FindFieldTemplate(controlId). Then if you need to you can cast it as an ITextControl to manipulate data.
Otherwise, try using this extension method to find the child control:
public static T FindControl<T>(this Control startingControl, string id) where T : Control
{
T found = startingControl.FindControl(id) as T;
if (found == null)
{
found = FindChildControl<T>(startingControl, id);
}
return found;
}
I found another solution, the other ones did not work.
In my case, I've copied Edit.aspx in /CustomPages/Devices/
Where Devices is the name of the table for which I want this custom behaviour.
Add this in Edit.aspx -> Page_Init()
DetailsDataSource.Selected += entityDataSource_Selected;
Add this in Edit.aspx :
protected void entityDataSource_Selected(object sender, EntityDataSourceSelectedEventArgs e)
{
Device device = e.Results.Cast<Device>().First();
// you have the object/row being edited !
}
Just change Device to your own table name.