DbConnectionDataProvider Klasse
Abstrakte Basisklasse für Datenprovider, die auf Daten einer IDbConnection zugreifen. Die konkreten Implementierungen in dieser Assembly sind die OleDbConnectionDataProvider Klasse, die OracleConnectionDataProvider Klasse und die SqlConnectionDataProvider Klasse. Sie können Ihre eigenen spezifischen Ableitungen hinzufügen, die IDbConnection verwenden, wenn Sie Zugriff auf die Datenbank-Schemainformationen für Ihren .NET Datenprovider haben (Tabellen und Relationen). Diese Klasse ist serialisierbar.
Um Ihre eigene Ableitung zu schreiben, überschreiben Sie die Init() Methode und übergeben alle Tabellen und Relationen an das protected Provider Member. Beachten Sie dazu das untenstehende Beispiel, um zu sehen wie dies in der SqlConnectionDataProvider Klasse gemacht wird. Solange Ihr Provider konform zu ISO SQL ist, sollten es nicht erforderlich sein weitere Änderungen vorzunehmen, die Basisklasse kümmert sich automatisch um das gesamte SQL Handling.
Überschreiben Sie die OnTranslateFilterSyntax Methode um das standardmäßige Verhalten für die Filtersyntax-Übersetzung zu ändern. Beachten Sie dazu das IAdvancedFiltering Interface für Details und beachten Sie ebenfalls das untenstehende Beispiel, um zu sehen wie diese Methode in der OracleConnectionDataProvider Klasse überschrieben wird. In diesem Fall wird nur die Behandlung der SUBSTRING SQL Funktion geändert, da der Name dieser Funktion in Oracle SUBSTR ist.
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;
}
}
Plattformen: Windows 10 (Version 21H2 - 22H2), Windows 11 (21H2 - 23H2), Windows Server 2016 - 2022
.NET: .NET Framework 4.8, .NET 6, .NET 8, .NET 9