How to read SQL Table data into a C# DataTable

sql

database-operations

best-practices

data-retrieval

byAnton Shumikhin·Nov 4, 2024

Import SQL data into a C# DataTable using SqlDataAdapter from System.Data.SqlClient. You'll formulate your SQL SELECT statement, define a connection string, and let SqlDataAdapter bring in the data and fill up the DataTable. Here's a basic implementation:

using System.Data;
using System.Data.SqlClient;

string connString = "Data Source=(Your Server); Initial Catalog=(Your Database); Integrated Security=True";
string sqlQuery = "SELECT * FROM (Your Table)";

using (SqlConnection conn = new SqlConnection(connString))
using (SqlDataAdapter adapter = new SqlDataAdapter(sqlQuery, conn))
{
    DataTable dt = new DataTable();
    adapter.Fill(dt); //Let's go fishing!
}

Replace (Your Server), (Your Database), and (Your Table) with your actual details. This will retrieve SQL data and allow you to use it in C#.

Connection is everything

A successful and secure connection lies at the heart of efficient data handling. The using statement is the tour guide here:

It initiates the connection.
It ensures the connection closes, even in the event of exceptions. "An open SQL connection walks into a bar, but the bar was null. Get the joke? Neither does the garbage collector."

SQL Commands and Parameters

Proficiency with CommandType can be a game-changer. Use CommandType.StoredProcedure when calling a stored procedure. You can also use SqlParameter to tackle SQL injection and simplify those complex queries:

string sqlQuery = "SELECT * FROM Table WHERE Column = @Value";
SqlCommand cmd = new SqlCommand(sqlQuery, conn);
cmd.Parameters.AddWithValue("@Value", someValue);
// It's like filling in a Mad Libs book

Handling exceptions is not an exception

Proper try-catch management around database operations creates a robust application ready to tackle unexpected hurdles.

Expanding scope: Best practices, tips and tricks

ADO.NET and its alternatives

While SqlDataAdapter belongs to the ADO.NET family, ORMs, like the Entity Framework Core, provide additional benefits including debug support and stronger type safety:

using (var context = new YourDbContext())
{
    var list = context.YourEntity.ToList();
    // Entity Framework - making C# wish it was Ruby since 2008
}

Efficiency in retrieving data

For the gigantic datasets, consider SqlDataReader.Read(), it streams rows and more memory-friendly than filling up a DataTable:

List<YourType> results = new List<YourType>();
SqlCommand cmd = new SqlCommand(sqlQuery, conn);
conn.Open();
using (SqlDataReader reader = cmd.ExecuteReader())
{
    while (reader.Read())
    {
        results.Add(new YourType {
            // Psst... it's like filling a bag one candy at a time
        });
    }
}
conn.Close();
// Always remember to close the door on your way out

Centralization of DB logic

Centralizing database logic into a single function boosts code reuse and maintenance. This function handles the opening and closing of connections and command executions, returning the desired results.

Responsiveness of your application

Using async methods from SqlCommand and SqlDataReader, the likes of ExecuteReaderAsync, can greatly enhance application responsiveness, particularly for GUI applications.

explain-codes / Sql / How to read SQL Table data into a C# DataTable

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