We have specified two where conditions in both linq and lambda queries. The first where clause checks for the income that is greater than 25,000 and the second where clause looks for the income that is less than 45,000. We can see there is just one income between 25000 and 40000. So we should be getting this as output from both queries.
Hi BDBodger, Yes, I have my datacontext set at class level: Private db As New ssopDataContext I will have alook at your code, However, I have coded the following which works: Public Sub searchStockNew ' NEW SEARCH STOCK METHOD USING THE NEW LINQ TO SQL db.Log = Console.Out ' SHOW SQL STATEMENT IN CONSOLE OUTPUT WINDOW Dim query As IQueryable( Of stock) = db.stocks query = query.Where( Function(I As stock) I.description. Contains( 'n')) ' USEING EXTENSIONS AND LAMBDA EXPRESSION The.Contains is like the 'LIKE' used within a SQL query. SQL generated by LINQ SELECT t0.stockID, t0.partNo, t0.description, t0.qty, t0.unitcost, t0.location, t0.min, t0.image, t0.date FROM dbo.stock AS t0 WHERE t0.description LIKE @p0 - @p0: Input NVarChar (Size = 3; Prec = 0; Scale = 0) %n% - Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.21022.8 Ron. Are you using a database object?
' outside of a procedure Dim DB As New MYDataContext ' from object designer ' in a sub or function Dim SearchQuery = From myitem in DB.stock where myitem.Description like '.' & msearch & '.' select myitem or Dim SearchQuery = From myitem in DB.stock where myitem.Description like '.' & msearch & '.' order by Description ' not needed or use another field select myitem or if not a DB Dim SearchQuery = From myitem in stock where myitem.Description like '.' & msearch & '.'
![Querying Querying](/uploads/1/2/5/4/125449837/543751884.png)
select myitem. Hi BDBodger, Yes, I have my datacontext set at class level: Private db As New ssopDataContext I will have alook at your code, However, I have coded the following which works: Public Sub searchStockNew ' NEW SEARCH STOCK METHOD USING THE NEW LINQ TO SQL db.Log = Console.Out ' SHOW SQL STATEMENT IN CONSOLE OUTPUT WINDOW Dim query As IQueryable( Of stock) = db.stocks query = query.Where( Function(I As stock) I.description.
Contains( 'n')) ' USEING EXTENSIONS AND LAMBDA EXPRESSION The.Contains is like the 'LIKE' used within a SQL query. SQL generated by LINQ SELECT t0.stockID, t0.partNo, t0.description, t0.qty, t0.unitcost, t0.location, t0.min, t0.image, t0.date FROM dbo.stock AS t0 WHERE t0.description LIKE @p0 - @p0: Input NVarChar (Size = 3; Prec = 0; Scale = 0) %n% - Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.21022.8 Ron. Yes well you seem to have a gasp of what to do and the output looks good. Your Contains statement is very much like the Like statement only there is no need for wildcards. I have not done any Lamda statements myself yet so your code is actually helpfull to me.
I found that the where clause was some what rigid in the tests I was doing. I couldn't see how to make it more dynamic. I think that Lambda expressions is what I was missing. I wanted to use a combobox to choose what field to search for the text in a textbox but had trouble with the where clause being able to accept a variable for the field name. Hi bdbodger, I am also new to Linq and currently developing test apps to convert my normal SQL statements to use LINQ. What I like about LINQ is that it maps the database tables into clases which fits the object oriented model. Tables become classes and the table columns become properties of that class.
Coding Linq queries requires less code and, due to intellisense, easier to code. I am just learning about Extensions, Anonymous types and Lambda expression within Linq. Here are some good learning sites that I have been using which may be of interest: ron.
By: Last Updated: 2008-07-07 Related Tips: Problem In a recent tip on, you have described how it can be used as a query language extension to both VB.NET and C#. How can we use LINQ to SQL in.NET applications to query SQL Server databases? Solution LINQ to SQL is a component of.NET Framework version 3.5 that provides a run-time infrastructure for managing relational data as objects. As most developers are used to the object-oriented paradigm, accessing data from a relational database requires understanding of relational paradigm. LINQ to SQL makes querying a SQL Server database as if it was an object and eliminate the need to write very complex SQL statements whenever necessary. It is also an OR/M (object-relational mapping) implementation that allows you to model a relational database using.NET classes. You can then run queries in the database as well as perform insert, update and delete actions to it.
Model your SQL Server databases using LINQ Visual Studio 2008 and the corresponding Express Editions come with a visual designer which makes it easy to model and visualize a database as a LINQ to SQL object model. Let's create a console project by following the steps outlined in the tip. We will name our Visual Studio project ConsoleLINQ2SQL and use the C# language. Next, let's add a new item in our project. Click on the Project menu and select Add New Item. From Visual Studio. This will do a couple of things.
First, it will add the namespace in the project. This assembly contains the framework implementation for LINQ to SQL and makes it easy to refer to SQL Server database objects as how developers do in object-oriented programming. Next, it gives you a object-relational designer where you can drag-and-drop database objects and it will create the corresponding. The designer will open up, displaying two separate panes, after adding the LINQ to SQL class in your project. The designer will create the corresponding classes necessary to translate your database into objects. Each table dragged into the designer surface will have a corresponding entity class.
Each instance of the entity class represents a row within the table. The arrows represent the relationships between the entity classes as defined by the primary key/foreign key constraints in the database. The direction of the arrows indicate whether the associations are one-to-one or one-to-many. Introducing the DataContext class The designer will create a corresponding DataContext class together with all of the entity classes that correspond to the tables in the database. This is done immediately after clicking the Save button within the designer surface. The class represents the main entry point for the LINQ to SQL framework and is the most important class. I refer to it as a proxy class responsible for representing how the database should look like from an object-oriented perspective.
We will be using this proxy class to query entities from the database as well as perform changes. The properties and methods of this proxy class correspond to the tables and stored procedures we have added, respectively. We will look at using stored procedures with LINQ to SQL in a future tip. Querying tables using LINQ Let's start writing some code inside the static void Main(string args). The first few lines of the output display the T-SQL query that LINQ generated and the provider used for the backend SQL Server database.
Mine displays SqlProvider( Sql2000) as I am using a SQL Server 2000 instance. You can also use SQL Profiler to capture the generated T-SQL queries. Notice the use of parameters in the query because of the existence of a where clause. LINQ to SQL generates parameterized queries in order to prevent SQL injection attacks thru the application.
Query Across Relationships Since the O/R model has generated the corresponding relationships for your classes, you can write queries that refer to those relationship properties. Let's say you wanted to retrieve all the OrderIDs and ContactName of all Customers based in Italy. You can write your query as shown below. Post a comment or let the author know this tip helped. All comments are reviewed, so stay on subject or we may delete your comment. Note: your email address is not published.
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