DbConnectionDataProvider Class
Abstract base class for data providers accessing the data of an IDbConnection. The concrete implementations in this assembly are the OleDbConnectionDataProvider Class, the OracleConnectionDataProvider Class and the SqlConnectionDataProvider Class. You can add your own custom IDbConnection consuming descendants if you can access the database schema information (tables and relations) for your .NET data provider. This class is serializable.
In order to write your own descendant, override the Init() method and pass all tables and relations to the protected Provider member. See the example below for how this is done in the SqlConnectionDataProvider Class. As long as your provider conforms to ISO SQL, you shouldn't need to change anything else, the base class takes care of the entire SQL handling automatically.
Override the OnTranslateFilterSyntax method in order to change the default handling for filter syntax translation. See IAdvancedFiltering Interface for details and see the example below for how this method is overridden in the OracleConnectionDataProvider Class. In this case, just the handling of the SUBSTRING SQL function is changed, as the name of this function is SUBSTR in Oracle.
protected override void Init()
{
if (Initialized)
return;
List<String> passedRelationNames = new List<string>();
Connection.Open();
try
{
DataTable dt = (Connection as SqlConnection).GetSchema("Tables");
foreach (DataRow dr in dt.Rows)
{
string tableSchema = dr["TABLE_SCHEMA"].ToString();
string tableType = dr["TABLE_TYPE"].ToString();
string parentTableName = dr["TABLE_NAME"].ToString();
switch (tableType)
{
case "BASE TABLE":
if ((SupportedElementTypes & DbConnectionElementTypes.Table) == 0)
continue;
break;
case "VIEW":
if ((SupportedElementTypes & DbConnectionElementTypes.View) == 0)
continue;
break;
default:
continue;
}
// pass table
SqlConnection newConnection = DbCommandSetDataProviderHelper.CloneConnection(Connection) as SqlConnection;
SqlCommand cmd = new SqlCommand("Select * From \"" + (String.IsNullOrEmpty(tableSchema) ? parentTableName+"\"" : tableSchema + "\".\"" + parentTableName) + "\"", newConnection);
Provider.AddCommand(cmd as IDbCommand, parentTableName);
// pass relations
string commandText = "sp_fkeys @pktable_name = '" + parentTableName + "'";
if (!String.IsNullOrEmpty(tableSchema))
{
commandText+= ", @pktable_owner = '"+tableSchema+ "'";
}
cmd = new SqlCommand(commandText, Connection as SqlConnection);
SqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
string childColumnName = reader.GetSqlString(7).ToString();
string parentColumnName = reader.GetSqlString(3).ToString();
// combined primary key, add key field to last relation on stack
if (reader.GetInt16(8) > 1)
{
IDataProvider providerInterface = (Provider as IDataProvider);
DbCommandTableRelation lastRelation = providerInterface.Relations[providerInterface.Relations.Count - 1] as DbCommandTableRelation;
lastRelation.ChildColumnName += '\t' + childColumnName;
lastRelation.ParentColumnName += '\t' + parentColumnName;
continue;
}
string childTableName = reader.GetSqlString(6).ToString();
string relName = reader.GetSqlString(2).ToString() + "2" + childTableName;
int relationIndex = 1;
string formatString = relName+"{0}";
while (passedRelationNames.Contains(relName))
{
relName = String.Format(formatString, relationIndex);
relationIndex++;
}
passedRelationNames.Add(relName);
Provider.AddRelation(relName, parentTableName, childTableName, parentColumnName, childColumnName);
}
reader.Close();
}
}
finally
{
Connection.Close();
Initialized = true;
}
}
Protected Overloads Overrides Sub Init()
If Initialized Then
Return
End If
Dim passedRelationNames As List(Of [String]) = New List(Of String)()
Connection.Open()
Try
Dim dt As DataTable = (TryCast(Connection, SqlConnection)).GetSchema("Tables")
For Each dr As DataRow In dt.Rows
Dim tableSchema As String = dr("TABLE_SCHEMA").ToString()
Dim tableType As String = dr("TABLE_TYPE").ToString()
Dim parentTableName As String = dr("TABLE_NAME").ToString()
Select Case tableType
Case "BASE TABLE"
If (SupportedElementTypes And DbConnectionElementTypes.Table) = 0 Then
Continue Select
End If
Exit Select
Case "VIEW"
If (SupportedElementTypes And DbConnectionElementTypes.View) = 0 Then
Continue Select
End If
Exit Select
Case Else
Continue Select
End Select
' pass table
Dim newConnection As SqlConnection = TryCast(DbCommandSetDataProviderHelper.CloneConnection(Connection), SqlConnection)
Dim cmd As New SqlCommand("Select * From """ + (If([String].IsNullOrEmpty(tableSchema), parentTableName + """", tableSchema + """.""" + parentTableName)) + """", newConnection)
Provider.AddCommand(TryCast(cmd, IDbCommand), parentTableName)
' pass relations
Dim commandText As String = "sp_fkeys @pktable_name = '" + parentTableName + "'"
If Not [String].IsNullOrEmpty(tableSchema) Then
commandText += ", @pktable_owner = '" + tableSchema + "'"
End If
cmd = New SqlCommand(commandText, TryCast(Connection, SqlConnection))
Dim reader As SqlDataReader = cmd.ExecuteReader()
While reader.Read()
Dim childColumnName As String = reader.GetSqlString(7).ToString()
Dim parentColumnName As String = reader.GetSqlString(3).ToString()
' combined primary key, add key field to last relation on stack
If reader.GetInt16(8) > 1 Then
Dim providerInterface As IDataProvider = (TryCast(Provider, IDataProvider))
Dim lastRelation As DbCommandTableRelation = TryCast(providerInterface.Relations(providerInterface.Relations.Count - 1), DbCommandTableRelation)
lastRelation.ChildColumnName += ControlChars.Tab + childColumnName
lastRelation.ParentColumnName += ControlChars.Tab + parentColumnName
Continue While
End If
Dim childTableName As String = reader.GetSqlString(6).ToString()
Dim relName As String = reader.GetSqlString(2).ToString() + "2" + childTableName
Dim relationIndex As Integer = 1
Dim formatString As String = relName + "{0}"
While passedRelationNames.Contains(relName)
relName = [String].Format(formatString, relationIndex)
System.Math.Max(System.Threading.Interlocked.Increment(relationIndex),relationIndex - 1)
End While
passedRelationNames.Add(relName)
Provider.AddRelation(relName, parentTableName, childTableName, parentColumnName, childColumnName)
End While
reader.Close()
Next
Finally
Connection.Close()
Initialized = True
End Try
End Sub
protected override void OnTranslateFilterSyntax(object sender, TranslateFilterSyntaxEventArgs e)
{
switch (e.ArgumentType)
{
case LlExpressionArgumentType.Function:
switch (e.Name.ToString().ToUpper())
{
case "MID$":
if (e.ArgumentCount == 2)
e.Result = (String.Format("(SUBSTR({0},{1}))", e.Argument1.ToString(), e.Argument2.ToString() + "+1"));
else
e.Result = (String.Format("(SUBSTR({0},{1},{2}))", e.Argument1.ToString(), e.Argument2.ToString() + "+1", e.Argument3.ToString()));
break;
case "LEFT$":
e.Result = (String.Format("(SUBSTR({0},0,{1}))", e.Argument1.ToString(), e.Argument2.ToString()));
break;
case "RIGHT$":
e.Result = (String.Format("(SUBSTR({0},-{1},{1}))", e.Argument1.ToString(), e.Argument2.ToString()));
break;
default:
e.Result = null;
break;
}
break;
default:
e.Result = null;
break;
}
}