oledb检索整个记录并从.accdb返回

Question

example of a return function that returns only string value, how do I return multiple values consisting of different data types in a single record by simply calling one function?

    public static string selectPassword(string user)
    {
        using (var connection = new OleDbConnection(connectionString))
        using (var command = connection.CreateCommand())
        {
            command.Parameters.AddWithValue("@user", user);
            command.CommandText = "SELECT [Password] FROM [Password_Table] WHERE Password_ID = [@user]";
            command.CommandType = CommandType.Text;

            connection.Open();

            var value = command.ExecuteScalar();

            return value == DBNull.Value ? null : value.ToString();
        }
    }

my record would be searched by Participant_Name, and would need to return Participant_Name, Participant_ID, Address, Contact_Number & Gender fields, all consisting of string, integers etc..

Answer 1

Create a data-type which consists of fields and properties that are able to hold the information that you want to retrieve.

Populate an instance of that type in your method, and return it.

Something like this, for instance:

public class Participant
{
   public int Id { get; private set; }
   public string Name {get; set;}
   public string Address {get; set; }


   public Participant( int id, string name, string address )
   {
       this.Id = id;
       this.Name = name;
       this.Address = address;
   }
}

public Participant GetParticipant( string name )
{
    using( var conn = new OleDbConnection (connectionString) )
    {
        using( var cmd = connection.CreateCommand() )
        {
              command.CommandText = "SELECT [Id], [Name], [Address] FROM Participant WHERE [name] LIKE @p_name";


               command.Parameters.Add ("@p_name", OleDbType.VarChar).Value = name + "%";

               using( var reader = command.ExecuteReader() )
               {
                    if( !reader.HasRows() ) return null;

                    reader.Read();

                    return new Participant (reader.GetString("Id"), reader.GetString("name"), reader.GetString("address"));
               }
        }
    }

}

Note: there can be syntax errors, since I haven't pulled it through the compiler, but I think you'll catch the drift.

Answer 2

for your needs you should return a DataRow object or an object array which you can get by calling .ItemArray on a DataRow

what you need to change in your method above is to use a DataAdapter and call its Fill method to fill a DataTable then return the first row of such DataTable, if any row is present.

you could also do this with the DataReader but then you should construct the array or objects container to return by yourself... I think dataRow.ItemArray is faster to code.