How to Retrieve Data from a SQL Server Database Using C#?

Retrieving Data from a SQL Server Database in C#

Introduction
Accessing data from a database is a crucial task in software development. This article explores how to retrieve data from a SQL Server database using C#.

Database Connectivity
To connect to a SQL Server database, use the SqlConnection class:

SqlConnection con = new SqlConnection("connectionString");

Selecting Data
To select data from the database, use a SqlCommand with the Select * from tablename query:

SqlCommand cmd = new SqlCommand("Select * from tablename", con);

Dynamic SQL Query
To retrieve data based on a parameter, use a parameterized query to avoid SQL injection:

cmd.CommandText = "Select * from tablename where firstname = @fName";
cmd.Parameters.AddWithValue("@fName", textBox1.Text);

Reading Data
To read the retrieved data, use a SqlDataReader:

using (SqlDataReader oReader = oCmd.ExecuteReader())
{
    while (oReader.Read())
    {
        // Access column data...
    }
}

Custom Object
For cleaner code, define a custom object to represent the data:

public class Person
{
    public string firstName;
    public string lastName;
}

Populating TextBoxes
To populate textboxes with the retrieved data, use the properties of the custom object:

Person x = SomeMethod("John");
txtLastName.Text = x.lastName;

Conclusion
This article demonstrated how to retrieve data from a SQL Server database in C# using a parameterized query and a custom object, providing a flexible and secure approach to data access.

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