How to Retrieve and Display SQL Server Data in a C# Windows Application?

Retrieve Data from SQL Server in C#

This guide will assist you in retrieving data from a SQL Server database using C# and a Windows application.

Establishing Database Connectivity

You have successfully established a connection to your SQL Server instance using the following code:

SqlConnection con = new SqlConnection("Data Source = .; Initial Catalog = domain; Integrated Security = True");

Retrieving Data

To retrieve data based on a value entered in a textbox (e.g., textbox1), you need to modify your code:

cmd.CommandText = "SELECT * FROM tablename WHERE firstname = @firstname";

Use parameterization to ensure the security of your query:

SqlParameter param = new SqlParameter("@firstname", SqlDbType.VarChar, 50);
param.Value = textbox1.Text;
cmd.Parameters.Add(param);

Populating Textboxes

You'd like to fill other textboxes with data based on the retrieved values. Here's a way to achieve this:

Create a class to represent a person (e.g., Person):

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int Age { get; set; }
}

Then, retrieve a person from the database using a parameterized method:

public Person GetPerson(string firstName)
{
    string connectionString = "Data Source = .; Initial Catalog = domain; Integrated Security = True";

    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        SqlCommand command = new SqlCommand("SELECT * FROM tablename WHERE firstname = @firstname", connection);
        command.Parameters.Add(new SqlParameter("@firstname", firstName));

        connection.Open();

        using (SqlDataReader reader = command.ExecuteReader())
        {
            if (reader.Read())
            {
                Person person = new Person
                {
                    FirstName = reader["firstname"].ToString(),
                    LastName = reader["lastname"].ToString(),
                    Age = (int)reader["age"]
                };

                return person;
            }
            else
            {
                return null; 
                // No matching person found
            }
        }
    }
}

Finally, populate your textboxes using the Person object:

textbox2.Text = person.LastName; // Replace "textbox2" with the name of your textbox
textbox3.Text = person.Age.ToString(); // Replace "textbox3" with the name of your textbox

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