I have created an Entity Model (.edmx) file with MySql database.I added some tables and then try to apply some linq to sql expression but for each expression it thorws an error "Object Reference not set to an instance of the object"
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whichever function I call, I get the same error : Object Reference not set to an instance of an object.
I m having one dataset underwhich i have two DataTables ie Contact & Sales Order.In this two table my ContactId field is primary key in both the tables. I cot some code similar to the following code. But when i copy this code two my .net application it me an error saying semicolun expected ,etc as shown bellow.
Error 37 Invalid expression term 'in'
Because of this i m not able to test the code. can any body tell me how can i achive it . I kust want to inner join this two tables & want to store the result in another data table.
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When I added Regular Expression validator on FileUpload Control, Page.IsValid returns false & Data is not Saved. I had used Regular Expression Validator like this:
asp:RegularExpressionValidator
ID="REVFileType"
runat="server"
ErrorMessage="*Invalid File(.bmp)"
ControlToValidate="FileUpload1"
Font-Bold="True"
SetFocusOnError="True"
ValidationExpression="^(([a-zA-Z]:)|(\{2}w+)$?)(\(w[w].*))(.jpg|.JPG|.gif)$"></asp:RegularExpressionValidator>.
I had used it to check if uploaded file is of extension .jpg|.JPG|.gif
I'm a newbie to this so bear with me. From what I've read online LINQ to Entity should see the relationships without having to specify the joins between multiple tables. I have a relationship that goes across 4 tables Employee, EmployeeDepartmentLink, EmployeeProjectLink, and Project. The idea is an employee can be in multiple departments and work on multiple projects with it being specified which department the employee is in for that project.
This is a C# MVC3 program connecting to a SQL database using VS 2010 Express.
I have no problem with running this query to find employees on a project:
[Code]....
Tring to do the reverse, finding projects that an employee worked on results in an error:
[Code]....
Error message: The specified type member 'EmployeeDepartmentLinks' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported. So I have 2 questions,
1) Why would it work in one direction and not the other? I've played around with it for a couple days with the same results.
2) Does it matter that my primary key and foreign keys are not named the same since all the relationships are connected in SQL? Ex: in Employee (EmployeePK)--(EmployeeFK) in EmployeeDepartmentLink Trying different stuff in LINQPad I was able to get the 2nd query to work if I specified all the joins which I thought was not neccesary with LINQ to Entity. I converted an SQL query that I made on the server into a LINQ query below which works.
Actually the controls are in a user control on an aspx page that also uses a master page (if that matters)
I defined a table in the skin file with TableHeaderRow, HeaderTableCell. I added some formatting to these entries. The table defined in the control is not being skinned by this definition. If I add a "CssClass" on the TableHeaderCell in the control, the formatting works fine. If I add the CssClass to the skin it doesn't work.
Skin file:
<asp:Table runat="server" SkinID="dataTable" BorderStyle="None" CellPadding="0" CellSpacing="0" CssClass="table">
var LateChangesTodate = (from lt in entities.Histories
where lt.RequestDate < dt && (lt.EmailDateA != null ? lt.CompleteDate.Value.AddHours(-48) > lt.EmailDateA : lt.CompleteDate.Value.AddHours(-48) > lt.RequestDate)
[code]...
And if so is there an example in vb .net? I want to add a linq result to the cache and then allow a mvc post to search the cache for better performance...every way I implement it I receive an object not referenced error...
I'm confused, maybe I shouldn't be doing it this way but the mvc post will be checking up to 2000 records and it would seem best not to have it querying the database everytime.
private void GetResults()
Use an Expression on a Linq Outer Join
I have an Entity class which has a Dictionary of fields called Data. Now I want to sort Entities by a field in Data. I was able to verify the Linq expression for using fields in a dictionary as e.Data["UserId"] as this seemed to work perfectly when I used LINQ to Objects. e.g. Entities.OrderBy(e => e.Data["UserId"])
However this same expression does not generate the correct NHibernate criteria and errors out finally with a NullReferenceException for propertyName at Hibernate.Loader.Criteria.CriteriaQueryTranslator.GetEntityName(ICriteria subcriteria, String propertyName)in CriteriaQueryTranslator.cs: line 541.
On debugging through NHibernate code, I figured that NHibernate.Linq.Visitors.MemberNameVisitor.GetMemberName(ICriteria rootCriteria, Expression expr) returns a null string in place of the field name after visiting expr using its visitor. This seems to be the cause of grief. I am using an older version of NHibernate (2.1). Are there any limitations in the NHibernate Linq visitor I should be aware of?
I have the following LINQ query which works correctly:
[Code]....
The following query, however causes an error:
[Code]....
"Could not translate expression 'Table(t_f2f_event).Where(e => ((e.EVT_START_DATE > Invoke(value(System.Func`1[System.Nullable`1[System.DateTime]]))) && (e.EVT_START_DATE < Invoke(value(System.Func`1[System.Nullable`1[System.DateTime]])))))' into SQL
and could not treat it as a local expression."
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 need to make a category filter. For this purpose I have two tables "Ingredient" and "Category"
My Category Table looks like this:
[Code]....
And my ingredient table:
[Code]....
I want to join the two tables so when the KategoriID match it should then return all from that category.
[Code]....
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I was trying to find out how I can join more than 2 tables using the LINQ-to-SQL syntax. For instance, joining 2 tables in SQL:
SELECT * FROM Table1 AS T1 INNER JOIN Table2 AS T2 ON T1.Key=T2.Column1WHERE T2.Key='17';
can be expressed as:
var Result = from T1 in DbContext.Table1 join T2 in DbContext.Table2 on T1.Key equals T2.ForeignKey where T2.Key=17 select new { T1, T2 };
But how would I join 3 or more tables using LINQ? For example:
SELECT * FROM (Table1 AS T1 INNER JOIN Table2 AS T2 ON T1.Key=T2.Column1) INNER JOIN Table3 AS T3 ON T3.Key=T2.Column2 WHERE T2.Key='37';
I've been searching and experimenting and I cannot seem to find any informraiton on this. One example I found involves putting the result for the frist join into a temp object, and then performing the second join. I'm not sure performance-wise if that's the same as doing a 3-table join directly using a single SQL statement.
<%# Eval("NAME").ToString() == "Edit" ? %>
<asp:ImageButton ID="imgEdit" runat="server" ImageUrl="../icons/icoedit.png" CommandName="Edit" CommandArgument='<%# Container.DataItemIndex %>' />
Error: Compiler Error Message: CS1525: Invalid expression term ',
I am not able to understand what is the problem with My sql ..as same query is run sucessfully while i use SQL Server 2005 whit out any Exception or error.........
Select Count( Date ) From Attendancemaster
Error in SELECT clause: expression near ')'.
Unable to parse query text.
this is very simple query run sucessfully in SQL Server 2005 but not in
MY SQL and giving Error..and the query on which any datetime avar comes in WHERE clause allso generate error always....?
I am using VS 2010 I've created LiNQ .dbml file via .. Model>Add New Item>Data>LINQ to SQL Clases I've put table on designer surface using drag & drop. I've done all this from one tutorial. There Is Mapping with arrows between tables in tutorial. How can i do this?
View 2 RepliesI have a partitioned db where several tables have the exact same structure. I'm able to query the tables using linq, but only by quering the individual tables 1 at a time and by using the explicit table name. For example at the moment, I have 8 tables so I have something similar to the following:
[Code]....
Is there any way, that based on a certain value (stringValue), I could determine which table to query and then code the linq query just once?
I have two tables:
Entity
ID (PK), int
Name
Descrip
Users
ID (PK)
EntityID, int (this is not connected to Entity table)
Now I am using LINQ to pull the records which has a Entity.ID = something. Which will show me couple of records in my GridView. Here is my LINQ statement:
protected void Page_Load(object sender, EventArgs e)
{
string getEntity = Request.QueryString["EntityID"];
int getIntEntity = Int32.Parse(getEntity);
OISEntityTestingDataContext db = new OISEntityTestingDataContext();
//OISLinqtoSQLDataContext db = new OISLinqtoSQLDataContext();
var tr =
from r in db.Users
join s in db.Entities on r.UserID equals s.ID
where s.ID == getIntEntity
select new
{
//To Show Items in GridView!
};
GridView1.DataSource = tr;
GridView1.DataBind();
}
Now here I am getting an error mesg on 'join' The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join What does that mean?
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:
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I try to write it in Linq so:
[Code]....
so I got error:
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and again I got an error:
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I am very new to Linq , i want to check if the PrintingAdminSetting table has rows in it and then if it has then i want to get the value and assign it to txtMaxJobs textbox
below is teh code
, please let me know teh syntax to check .
var DC = new ServiceDataContext();
var rec = DC.PrintingAdminSetting.Where("").First();
txtMaxJobs.Text = rec.ParaName.ToString();
I have a couple tables that are kind of unrelated - id like to search through both of them and create a type that i can sift through later
something like this doesnt work
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I basically want to create a list of "AnimalSearchResults" that contains all dogs and all cats that have that name Whats the best way to do something like this?
Here's my DB structure:
I have three tables.
User, Details, Optional
User has fields: ID, FirstName, LastName
Details has fields: ID, MyDetails1, MyDetails2, User_ID
Optional has fields: ID, MyOptions1, MyOptions2, User_ID
There is a 1 to many relationship with User & Detail (User ID & Detail User_ID)
There is a 1 to many relationship with User & Optional (User ID & Optional User_ID)
With that said, one user can have many details and/or many optionals
Now I'm trying to build a linq query that will say:
"where user id = x, select FirstName, LastName, all MyDetails1 from every record where User_ID == x, all MyOptions1 from every record where User_ID == x"
After the merge I should have one string that lists the distict user & all of their many fields:
FirstName + LastName + (MyDetails1 + MyDetails1 + MyDetails1..etc) + (MyOptions1 + MyOptions1)
Anyone try this before?
I tried this with JOIN but this doesn't do the trick for what I'm looking for.
So if I had 3 MyDetails records associated with ID == 2, I would get three results like:
John Doe MyDetails_X
John Doe MyDetails_Y
John Doe MyDetails_Z
Using Linq to Sql how do i group the following 2 tables.
Orders Table:
CustomerID | Name |Date
1 | order1 | 2010-01-01
2 | order2 | 2010-01-01
2 | order3 | 2010-04-01
Calls Table:
CustomerID | Name |Date
1 | call1 | 2010-01-01
3 | call2 | 2010-06-01
2 | call3 | 2010-05-01
I want to group the two tables by date , Result:
Date | Orders | Calls
2010-01-01 | 2 | 1
2010-04-01 | 1 | 0
2010-05-01 | 0 | 1
2010-06-01 | 0 | 1
i know how to group a single table ,from o in Orders group o by o.Date.Date into og select new {Date = og.Key,Orders= og.Count()};
The main problem is that I recieve the following message:
"base {System.SystemException} = {"Unable to create a constant value of type 'BokButik1.Models.Book-Author'. Only primitive types ('such as Int32, String, and Guid') are supported in this context."}"
based on this LinQ code:
[Code]....
How shall I solve this problem to get a class instance that contain with property title and Book-AuthorID?I also have tried making some dummy by using "allbooks" relation with Code Samples from the address
http://www.hookedonlinq.com/JoinOperator.ashx. Unfortunately, still same problem.
I also have taken account to Int32 due to entity framework http://msdn.microsoft.com/en-us/library/bb896317.aspx. Unfortunatley, still same problem.
Using database with 3 tables and one of them is a many to many relationship. This database is used in relation with entity framework
Book-Author
Book-Author (int)
BookID (int)[code]....
I was wondering how Linq to Sql determines which tables to write to when given primary/foreign Key relationships. I can (hopefully) better explain using an example. I have the following tables:
Customer CustomerStatus CustomerType CustomerAddresses
Therefore I have a Customer Entity, a CustomerStatus entity, a CustomerType Entity and a List of CustomerAddresses. In my code, I load up the Customer Entity and the List of CustomerAddresses because that's all I need. For some reason Linq to Sql is trying to insert a new Customer Status record. I have no idea why its doing this.
Can anyone please explain to me how linq to sql determines which table(s) will be written to based on the entities above?
