How do I extract data from a DataTable?

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I have a DataTable that is filled in from an SQL query to a local database, but I don't know how to extract data from it. Main method (in test program):

static void Main(string[] args)
{
    const string connectionString = "server=localhost\\SQLExpress;database=master;integrated Security=SSPI;";
    DataTable table = new DataTable("allPrograms");

    using (var conn = new SqlConnection(connectionString))
    {
        Console.WriteLine("connection created successfuly");

        string command = "SELECT * FROM Programs";

        using (var cmd = new SqlCommand(command, conn))
        {
            Console.WriteLine("command created successfuly");

            SqlDataAdapter adapt = new SqlDataAdapter(cmd);

            conn.Open(); 
            Console.WriteLine("connection opened successfuly");
            adapt.Fill(table);
            conn.Close();
            Console.WriteLine("connection closed successfuly");
        }
    }

    Console.Read();
}

The command I used to create the tables in my database:

create table programs
(
    progid int primary key identity(1,1),
    name nvarchar(255),
    description nvarchar(500),
    iconFile nvarchar(255),
    installScript nvarchar(255)
)

How can I extract data from the DataTable into a form meaningful to use?

ado.net sql c#
7 Answers

The simplest way to extract data from a DataTable when you have multiple data types (not just strings) is to use the Field<T> extension method available in the System.Data.DataSetExtensions assembly.

var id = row.Field<int>("ID");         // extract and parse int
var name = row.Field<string>("Name");  // extract string

From MSDN, the Field<T> method:

Provides strongly-typed access to each of the column values in the DataRow.

This means that when you specify the type it will validate and unbox the object.

For example:

// iterate over the rows of the datatable
foreach (var row in table.AsEnumerable())  // AsEnumerable() returns IEnumerable<DataRow>
{
    var id = row.Field<int>("ID");                           // int
    var name = row.Field<string>("Name");                    // string
    var orderValue = row.Field<decimal>("OrderValue");       // decimal
    var interestRate = row.Field<double>("InterestRate");    // double
    var isActive = row.Field<bool>("Active");                // bool
    var orderDate = row.Field<DateTime>("OrderDate");        // DateTime
}

It also supports nullable types:

DateTime? date = row.Field<DateTime?>("DateColumn");

This can simplify extracting data from DataTable as it removes the need to explicitly convert or parse the object into the correct types.

user_96650210
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