Mapping SQL Server Query Results to a DataGridView in .NET

By:Artemakis Artemiou | Last Updated: 2018-12-27 || Related Tips:More > Application Development

Problem

Inprevious tips that I have written about SQL Server and .NET, we've learned how to get started with .NET and SQL Server data access. To this end, we've learned how to connect to SQL Server from a C# program and run a simple query, as well as how to query SQL Server tables from .NET and process the results. Moreover, we've learned how to work with SQL Server stored procedures and functions from within .NET applications. In this tip, we are going to see something different. We are going to create a .NET windows Forms Application, retrieve query results from a SQL Server database, and finally display these results in a DataGridView control.

Solution

Raw data is just data. In order to transform data to knowledge, you need to properly process them and present them. One way towards this, is to use Graphical User Interface controls and data visualization. For example, in .NET, one such control is DataGridView .

The DataGridView control in .NET, displays data in a customizable grid. For example, you can retrieve data from SQL Server, i.e. via a query, and display the data on the DataGridView control in a Windows Forms .NET application. Then, using the DataGridView control's features and properties, you can further process the data and customize their display (i.e. sort them, etc.).

In this tip, we are going to perform the below:

Create a simple Windows Forms .NET C# application along with including a DataGridView control Run a query against a sample database and retrieve the results Display the results on a DataGridView control Customize the DataGridView control Sample Database and Data

In this tip's examples, I will be using the database " SampleDB ", which is on a test SQL Server 2017 named instance on my local machine, called " SQL2K17 ". This database, is the same I used in my previous .NET Application Development tips .

Here's a screenshot of the SQL Server instance, as it can be seen in SSMS:

The sample database has two tables named " employees " and " location" and you can see their content on the above screenshot.

Query for Retrieving Sample Data

The query that will be used for retrieving the sample data is:

SELECT e.id,
e.code,
e.firstName,
e.lastName,
l.code AS locationCode,
l.descr AS locationDescr
FROM dbo.employees e
INNER JOIN dbo.location l
ON l.id = e.locationID;
GO

If we execute the above SQL query in SSMS against our sample database and tables, this is what we get:

As you can see, the SQL query returns 4 rows with the data presented in the above screenshot.

Create the Windows Forms .NET C# application and add a DataGridView control

Let's start a new "Windows Forms App" project in Visual Studio 2017 , name it " TestApp5 ", and save it in the folder "c:\temp\demos":

Right after the above action, out Windows Forms project opens and the workspace is ready for us to add some GUI controls and write some code!

So, after I increase the size of my main form a bit, from the toolbox on the left I drag a drop a DataGridView control, and a button. Next, I increase the size of the DataGridView control and set the "Text" property for the button (see the "Properties" dialog on the right after you select the button control) to "Refresh". Also, to make code look prettier and more manageable, I change the button's "Name" property to "btnRefresh" and the DataGridView's name to "grdData".

After the above, this how my Windows form looks:

The DataGridView Control

There two ways to set the columns of a DataGridView control in .NET. These are:

Set static columns by populating the "Columns" collection in the control's properties. Write code that dynamically creates the columns.

Since I find the second option, that is dynamically creating the columns, more robust, I will let my code create them.

Run Query against the Sample Database, Retrieve the Results and Populate the DataGridView Control

Now let's write the query and relevant C# code that retrieves the data from the "SampleDB" database. The code will be executed when the "Refresh" button is clicked. So, on our workspace, we double-click on the "Refresh" button in order to navigate to the code editor, and more explicitly, in the "Refresh" button's click event code handling block:

The code to be added here, is similar to the code I wrote in my previous .NET development tips. To this end, on the very top of my code, I add the library System.Data.SqlClient:

using System.Data.SqlClient;

Then, in the " btnRefresh_Click " method I add the below code:

private void btnRefresh_Click(object sender, EventArgs e)
{
//set the connection string
string connString = @"Server =.\SQL2K17; Database = SampleDB; Trusted_Connection = True;";
try
{
//sql connection object
using (SqlConnection conn = new SqlConnection(connString))
{
//retrieve the SQL Server instance version
string query = @"SELECT e.id,
e.code,
e.firstName,
e.lastName,
l.code AS locationCode,
l.descr AS locationDescr
FROM dbo.employees e
INNER JOIN dbo.location l
ON l.id = e.locationID;";
//define the SqlCommand object
SqlCommand cmd = new SqlCommand(query, conn);
//Set the SqlDataAdapter object
SqlDataAdapter dAdapter = new SqlDataAdapter(cmd);
//define dataset
DataSet ds = new DataSet();
//fill dataset with query results
dAdapter.Fill(ds);
//set DataGridView control to read-only
grdData.ReadOnly = true;
//set the DataGridView control's data source/data table
grdData.DataSource = ds.Tables[0];
//close connection
conn.Close();
}
}
catch (Exception ex)
{
//display error message
MessageBox.Show("Exception: " + ex.Message);
}
}

Let's discuss the above code in order to better understand it.

As you can see, just like the rest of my .NET tips, everything takes place inside the "using (SqlConnection conn = new SqlConnection(connString))" code block.

So, within that code block, I define the query to be executed against my SQL Server conn