What will be the equivalent GroupJoin lambda expression in LINQ when I do this.
Dim fruit_salad = (From fruits In _DataContext_Fruits _
Group Join fruitRipe In _DataContext_FruitRipe On fruitRipe.fID Equals fruits.fID Into Group
From fruitty_lecious In Group.DefaultIfEmpty() _
[code]...
I'm trying to build a linq2Entity/gridview function for a forum, that draws data from multible tables.The result should be: Get the latest 10 threads that user(xx) has replyed in, that is not disabled or has a subject that is not allowed.Include information on the last post, thread owner user, and last post user, in each thread.
ere is my code... is returns the correct threads and some that should not be there.
[Code]....
I have a dictionary with integers representing ProductId's.
I want to get all the Products that are listed in this dictionary. What is the best way of doing this?
I have tried the following which doesnt work:
gvBasket.DataSource = ent.Products.Where(x => x.ProductId in Dic.Keys);
i have the following, which works:
@{Html.RenderAction("Detail", "Help", new { pageName = "press" });}
But instead i'd like to use a lambda expression to get away from the string bits. I tried using the following (which is the nearest approximation i could figure based on my limited knowledge of the engine):
@{Html.RenderAction<HelpController>(x => x.Detail("press"));}
But i get the following error:
The non-generic method 'System.Web.Mvc.Html.ChildActionExtensions.RenderAction(System.Web.Mvc.HtmlHelper, string, string, System.Web.Routing.RouteValueDictionary)' cannot be used with type arguments
However, i'm reading in the Apress MVC 2.0 book that it is in fact declared as a method that takes type arguments. Am i missing an assembly reference, or has it not been included in the MVC 3.0 Preview 1 build?
I have two lists. lst contains ViewState Data i.e All the records of the gridview & second lstRank contains the list of integer(i.e ID) for only those records which are marked as checked (i.e Gridview contains a columns for checkbox). Now i want to update the lst bool status depending upon integer ID of lstRank. How it can be achieved by lambda expression
List<Tuple<int, string, bool>> lst = (List<Tuple<int, string,bool>>)ViewState["gvData"];
List<int> lstRank = gvDetails.Rows.OfType<GridViewRow>().Where(s => ((CheckBox)s.FindControl("chkSelect")).Checked)
.Select(s => Convert.ToInt32(((Label)s.FindControl("lblRankCD")).Text)).ToList();
I Use entity framework 4.
Here is my model
Language
LangID
LangName
Product
PrdID
IsActive
ProductText
PrdID
LangID
Text
Category
CatID
IsActive
CategoryText
CatID
LangID
Text
Each time I want the text for one of these model, I execute this lambda expression p=> p.LangID == 1
Is it possible to create a generic lambda expression function that all of these model can use.?
To write a join query with or condition. It means a query has two inner join, here it is possible to fetch the records, if one inner join is true and other is false. I got a record when only two join conditions are true.
View 1 RepliesI did a small experiment to test whether lamdba expression can retrieve faster results than foreach statement. but, Lambda failed
[Code]....
why lambda is slower than foreach. This may be a drawback of lambda expression
I am selecting the checked rows from Gridview. To achieve this i have written a lambda expression using dynamic keyword.
var dn = gvLoans.Rows.OfType<dynamic>().Where(s => s.FindControl("chkSelect").Checked == true).Select(s => s.FindControl("lblCD")).ToList();
I want the output of this in List. Can it be achieved by extending the query or i have to write foreach statement.
I need to get two fields from a database table (retrieved using linq-to-sql), one field is a datetime (and is a fixed field) and the other is always a decimal, but the field can be different.
The table holds currency data which is processed twice a day and in different currencies so could have fields such as AM_USD, PM_USD, AM_EUR etc. And I need to get data such as a list of the date against PM_USD or the date against AM_EUR.
I would like to be able to call the data using a lambda expression for example (this is a stripped out example):
data = TableData.Select(x=>new {x.DateTimeAdded, x.[**field name as string**]});
I have been trying to write a function to do this, and am failing dismally.
The closest I have managed is:
private Func<TableData, KeyValuePair<DateTime, decimal>> CreateSelect(string FieldName)
{
var parameterExp = Expression.Parameter(typeof(TableData), "sel");
var dateParameter = Expression.Parameter(typeof(DateTime), "DateTimeAdded");
var fieldParameter = Expression.Parameter(typeof(decimal), FieldName);
ConstructorInfo constructorInfo = typeof(KeyValuePair<DateTime, decimal>).GetConstructor(new[] { typeof(DateTime), typeof(decimal) });
NewExpression constructExpression = Expression.New(constructorInfo, new ParameterExpression[] { dateParameter, fieldParameter});
var lambda = Expression.Lambda<Func<TableData, KeyValuePair<DateTime, decimal>>>( constructExpression, parameterExp);
return lambda.Compile();
}
Which fails with "System.InvalidOperationException: Lambda Parameter not in scope".
I'm sure I missing something obvious, or going about it wrong way.
I'm new to LINQ and EF and I seem to be having trouble working this out.
I have a many-to-many relationship between my Location and Region tables. When adding or editing a Location, my interface allows the user to check any number of related Regions. If they click OK, I need to add any new relationships that were checked, and delete any existing relationships that have been unchecked. My basic code is shown below.
However, this code doesn't work. Lower down, the line location.Regions.Contains(region) returns false even when the location already is related to the region. The issue appears to be because the region is from my populated listbox that was initialized earlier and is no longer part of the current EF context. But if I try and add it, I get an error that there is already a Region with that ID.
It seems like what I want to do is change this line to something like location.Regions.Contains((r) => r.RgnID == region.RgnID) so I'm only testing for a particular ID. But this gives me the error "Cannot convert lambda expression to type 'TrailCalendar.Region' because it is not a delegate type."
I don't understand this error but, either way, I'm not sure how I can test if the relationship already exists without reloading a bunch of data, which I'd like to avoid.
I am new to LINQ to XML in .net(C#, asp.net). I want to know more about Lambda expressions. I am using Lambada expression with the following query.
count = FieldRoot.Element("USER").Element("MM")
.Descendants("MMMS")
.Where(a => a.Attribute("ID").Value == MID)
.SelectMany(b => b.Descendants("ABC")).Count();
how the Lambda expression work specially in case of parameters (in the above case a & b) ? What is the basic concept of parameters in Lambda expression ? Can we use the names of the variables defined outside of the query instead of a & b ? which elements a & b represent in the above case represent ? Can we pass parameters from outside in the query ? If we can pass parameters from outside query then how it will be done? If you give me any other example instead of the above query to understand the concept of parameter in Lambda expression.
I have T_articles to save the articles.
each article has authorCode , and categoryCode.
each article can be modified by the author several times.
and I save every modification in the T_articles in a difference row.
now I want to dislpay for each autor:
author name, article name , article category's name, last modified date
In SQL I should to it like that:
[Code]....
I try to write it in Linq so:
[Code]....
so I got error:
[Code]....
and again I got an error:
[Code]....
I have this group-join syntax but I couldn't get the distinct value from the relational tables below.
Table_1
key_1 t1_value
1 Food
2 Sports
3 Leisure
4 Trip
5 Zoo
Table_2
key_2 key_1 t2_boolean
15 1 True
16 1 True
17 1 True
18 2 True
19 2 True
20 2 False
desire result:
[code]...
private void GetResults()
Use an Expression on a Linq Outer Join
Below is my query for Access.. Which it is saying Error Message ( Join expression Not Supported )
SELECT PatientMst.Name AS [Patient Name],REPLACE(REPLACE(RIGHT('0'+LTRIM(RIGHT(CONVERT(varchar,Appoint.Time,100),7)),7),'AM',' AM'),'PM',' PM') AS [Time],Appoint.Ptid,Appoint.Aptid,replace(convert(varchar,Appoint.Date,106),' ','-') as [Date] FROM PatientMst
INNER JOIN Appoint ON PatientMst.Ptid = Appoint.Ptid and Appoint.Date = ('03/21/2010')
I get this error: "Cannot convert lambda expression to type 'string' because it is not a delegate type" - keyword select become underlined in blue.
[code]....
Above code should displays drop list of employees first name and last name in a combo box
let me know the types of joins available in SQL, so far i've used only Inner joins and left joins.
But have been clear and comfortable using inner joins only.
give me a more clear picture on all the types of joins available and their importance.
I have three tables nameTbl contains the following columns: BarID, Name, Description locTbl contains locID and Location namelocationTbl contains BarID(from the nameTbl) and locID(from the locTbl)
View 2 RepliesI have a gridview with a sqldatasource with SelectCommand as below:
[Code]....
but it's not workling.....
I need to join some tables to get the matching records. I often have to ask around to see how certain tables could be joined. Is there any way to query the information schema or some thing else to see what columns/values match in certain tables in order to figure out how tables should be joined.
View 4 RepliesAnyone know if it's possible to inner join tables using two different connection strings? I'm using vb.
View 3 Repliesi have two queries they are:
query1:
select CustID,NoOfChits from tblCust1 where [Group]='A' and CustID='a001'
query2:
select count(TKCustID) as Taken from tblAuctionGroup where [Group]='A' and TKCustID='a001'
Results of 1st query was:
----------
CustID NoOfChits
a001 2
Results of 2nd query was:
----------
Taken
4
But i want to like below:
--------------------------
CustID NoOfChits Taken
a001 2 4
in the above queries, 1st query displayed two columns and 2nd query displayed one column. but i would like to append the both results in single table or single record, i mean all results should be in same row in same result.
I can join with a regular SQL table fine but this won't work:
SELECT normalTbl.*, tmp.fld1 FROM normalTbl
LEFT JOIN #Temp tmp ON tmp.joinID = normalTbl.joinID
All tmp.fld1 values are shown as NULL even though fld1 contains valid values and the joinID matches the normalTbl (when I call SELECT * from #Temp). If I do the same exact thing with a regular table, fld1 shows the correct value. What am I doing wrong?
I am trying to update a Single Record in a table. I also trying to join columns of that single record with another table to update prices the prices of that record.
Here is my current query.
[Code]....