ADO.NET 4 快速上手（3）——DataReader读数据

三、DataReader读数据

1.   执行SQL读表

string connectionString = "Data Source=(local);Initial Catalog=Northwind;Integrated Security=true";

// Provide the query string with a parameter placeholder.
string queryString =
"SELECT ProductID, UnitPrice, ProductName from dbo.products WHERE UnitPrice > @pricePoint "
    + "ORDER BY UnitPrice DESC;";

// Specify the parameter value.
int paramValue = 5;

// Create and open the connection in a using block. This
// ensures that all resources will be closed and disposed
// when the code exits.
using (SqlConnection connection = new SqlConnection(connectionString))
{
    // Create the Command and Parameter objects.
    SqlCommand command = new SqlCommand(queryString, connection);
    command.Parameters.AddWithValue("@pricePoint", paramValue);

    // Open the connection in a try/catch block.
    // Create and execute the DataReader, writing the result
    // set to the console window.
    try
    {
        connection.Open();
        SqlDataReader reader = command.ExecuteReader();
        while (reader.Read())
        {
            Console.WriteLine("\t{0}\t{1}\t{2}",
            reader[0], reader[1], reader[2]);
        }

        reader.Close();
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }

    Console.ReadLine();
}

2.调有参存储过程，返回表

using (SqlConnection connection = new SqlConnection(connectionString))
{
    // Create the command and set its properties.
    SqlCommand command = new SqlCommand();
    command.Connection = connection;
    command.CommandText = "SalesByCategory";
    command.CommandType = CommandType.StoredProcedure;

    // Add the input parameter and set its properties.
    SqlParameter parameter = new SqlParameter();
    parameter.ParameterName = "@CategoryName";
    parameter.SqlDbType = SqlDbType.NVarChar;
    parameter.Direction = ParameterDirection.Input;
    parameter.Value = categoryName;

    // Add the parameter to the Parameters collection.
    command.Parameters.Add(parameter);

    // Open the connection and execute the reader.
    connection.Open();
    SqlDataReader reader = command.ExecuteReader();

    if (reader.HasRows)
    {
        while (reader.Read())
        {
            Console.WriteLine("{0}: {1:C}", reader[0], reader[1]);
        }
    }
    else
    {
        Console.WriteLine("No rows found.");
    }

    reader.Close();
}