C# 4 and .NET 4

a Custom resource reader ❘ 599
A resource reader has to implement the interface IResourceReader . This interface defi nes the methods
Close() and GetEnumerator() to return an IDictionaryEnumerator that returns keys and values for the
resources. In the implementation of GetEnumerator() , create a Hashtable where all keys and values for
a specifi c language are stored. Next, you can use the SqlConnection class in the namespace System.Data
.SqlClient to access the database in SQL Server. Connection.CreateCommand() creates a SqlCommand()
object that you use to specify the SQL SELECT statement to access the data in the database. If the language is
set to de , the SELECT statement is SELECT [key], [de] FROM Messages . Then you use a SqlDataReader
object to read all values from the database and put them into a Hashtable . Finally, the enumerator of the
Hashtable is returned.
For more information about accessing data with ADO.NET, see Chapter 30, “ Core
ADO.NET.”
public System.Collections.IDictionaryEnumerator GetEnumerator()
{
Dictionary < string, string > dict = new Dictionary < string, string > ();
SqlConnection connection = new SqlConnection(connectionString);
SqlCommand command = connection.CreateCommand();
if (String.IsNullOrEmpty(language))
language = "Default";
command.CommandText = "SELECT [key], [" + language + "] " +
"FROM Messages";
try
{
connection.Open();
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
if (reader.GetValue(1) != System.DBNull.Value)
{
dict.Add(reader.GetString(0).Trim(), reader.GetString(1));
}
}
}
reader.Close();
}
catch (SqlException ex)
{
if (ex.Number != 207) // ignore missing columns in the database
throw; // rethrow all other exceptions
}
finally
{
connection.Close();
}
return dict.GetEnumerator();
public void Close()
{
}
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