The CData ADO.NET Provider for Azure Cosmos DB implements two ADO.NET interfaces you can use to retrieve data from Azure Cosmos DB: CosmosDBDataAdapter and CosmosDBDataReader objects. Whereas CosmosDBDataAdapter objects retrieve a single result set of all the data that matches a query, CosmosDBDataReader objects fetch data in subset increments as needed.

Using the CosmosDBDataReader

The CosmosDBDataReader retrieves data faster than the CosmosDBDataAdapter because it can retrieve data in pages. As you read data from the CosmosDBDataReader, it periodically requests the next page of results from the data source, if required. This causes results to be returned at a faster rate. The following example selects all the columns from the [CData].[Entities].Customers table:

C#

string connectionString = "AccountEndpoint=myAccountEndpoint;AccountKey=myAccountKey;";

using (CosmosDBConnection connection = new CosmosDBConnection(connectionString)) {
  CosmosDBCommand cmd = new CosmosDBCommand("SELECT * FROM [CData].[Entities].Customers", connection);
  
  CosmosDBDataReader rdr = cmd.ExecuteReader();

  while (rdr.Read()) {
    Console.WriteLine(String.Format("\t{0} --> \t\t{1}", rdr["City"], rdr["CompanyName"]));
  }
}

VB.NET

Dim connectionString As String = "AccountEndpoint=myAccountEndpoint;AccountKey=myAccountKey;"

Using connection As New CosmosDBConnection(connectionString)
  Dim cmd As New CosmosDBCommand("SELECT * FROM [CData].[Entities].Customers", connection)

  Dim rdr As CosmosDBDataReader = cmd.ExecuteReader()

  While rdr.Read()
    Console.WriteLine([String].Format(vbTab & "{0} --> " & vbTab & vbTab & "{1}", rdr("City"), rdr("CompanyName")))
  End While
End Using