Create a Windows Form to search data
A common application scenario is to display selected data on a form. For example, you might want to display the orders for a specific customer or the details of a specific order. In this scenario, a user enters information into a form, and then a query is executed with the user's input as a parameter; that is, the data is selected based on a parameterized query. The query returns only the data that satisfies the criteria entered by the user. This walkthrough shows how to create a query that returns customers in a specific city, and modify the user interface so that users can enter a city's name and press a button to execute the query.
Using parameterized queries helps make your application efficient by letting the database do the work it is best at — quickly filtering records. In contrast, if you request an entire database table, transfer it over the network, and then use application logic to find the records you want, your application can become slow and inefficient.
You can add parameterized queries to any TableAdapter (and controls to accept parameter values and execute the query), using the Search Criteria Builder dialog box. Open the dialog box by selecting the Add Query command on the Data menu (or on any TableAdapter smart tag).
Tasks illustrated in this walkthrough include:
Creating and configuring the data source in your application with the Data Source Configuration wizard.
Setting the drop type of the items in the Data Sources window.
Creating controls that display data by dragging items from the Data Sources window onto a form.
Adding controls to display the data on the form.
Completing the Search Criteria Builder dialog box.
Entering parameters into the form and executing the parameterized query.
This walkthrough uses SQL Server Express LocalDB and the Northwind sample database.
If you don't have SQL Server Express LocalDB, install it either from the SQL Server Express download page, or through the Visual Studio Installer. In the Visual Studio Installer, you can install SQL Server Express LocalDB as part of the Data storage and processing workload, or as an individual component.
Install the Northwind sample database by following these steps:
In Visual Studio, open the SQL Server Object Explorer window. (SQL Server Object Explorer is installed as part of the Data storage and processing workload in the Visual Studio Installer.) Expand the SQL Server node. Right-click on your LocalDB instance and select New Query.
A query editor window opens.
Copy the Northwind Transact-SQL script to your clipboard. This T-SQL script creates the Northwind database from scratch and populates it with data.
Paste the T-SQL script into the query editor, and then choose the Execute button.
After a short time, the query finishes running and the Northwind database is created.
Create the Windows Forms application
Create a new Windows Forms App project for either C# or Visual Basic. Name the project WindowsSearchForm.
Create the data source
This step creates a data source from a database using the Data Source Configuration wizard:
To open the Data Sources window, on the Data menu, click Show Data Sources.
In the Data Sources window, select Add New Data Source to start the Data Source Configuration wizard.
Select Database on the Choose a Data Source Type page, and then click Next.
On the Choose your Data Connection page do one of the following:
If a data connection to the Northwind sample database is available in the drop-down list, select it.
Select New Connection to launch the Add/Modify Connection dialog box.
If your database requires a password, select the option to include sensitive data, and then click Next.
On the Save connection string to the Application Configuration file page, click Next.
On the Choose your Database Objects page, expand the Tables node.
Select the Customers table, and then click Finish.
The NorthwindDataSet is added to your project, and the Customers table appears in the Data Sources window.
Create the form
You can create the data-bound controls by dragging items from the Data Sources window onto your form:
Expand the Customers node in the Data Sources window.
Drag the Customers node from the Data Sources window to your form.
A DataGridView and a tool strip (BindingNavigator) for navigating records appear on the form. A NorthwindDataSet, CustomersTableAdapter, BindingSource, and BindingNavigator appear in the component tray.
Add parameterization (search functionality) to the query
You can add a WHERE clause to the original query using the Search Criteria Builder dialog box:
Select the DataGridView control, and then choose Add Query on the Data menu.
Type FillByCity in the New query name area on the Search Criteria Builder dialog box.
WHERE City = @Cityto the query in the Query Text area.
The query should be similar to the following:
SELECT CustomerID, CompanyName, ContactName, ContactTitle, Address, City, Region, PostalCode, Country, Phone, Fax FROM Customers WHERE City = @City
Access and OLE DB data sources use the question mark ('?') to denote parameters, so the WHERE clause would look like this:
WHERE City = ?.
Click OK to close the Search Criteria Builder dialog box.
A FillByCityToolStrip is added to the form.
Test the application
Running the application opens your form and makes it ready to take the parameter as input:
Press F5 to run the application.
Type London into the City text box, and then click FillByCity.
The data grid is populated with customers that meet the criteria. In this example, the data grid only displays customers that have a value of London in their City column.
Depending on your application requirements, there are several steps you may want to perform after creating a parameterized form. Some enhancements you could make to this walkthrough include:
Adding controls that display related data. For more information, see Relationships in Datasets.
Editing the dataset to add or remove database objects. For more information, see Create and configure datasets.
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