علت خطای access violation

[vb.net2008]

سلام مشکل قطعه کد زیر چیه که پیغام 72807 میده

var TPic: TBlobField;
begin
TPic:=TBlobField.Create(self);
TPic.LoadFromFile(OpenDialog1.FileName);

[BORHAN TEC]

نحوه استفاده از TBlobFiled به شکل دیگری است. برای درک این مطلب به مثال زیر توجه کنید:
var
myBlobField : TBlobField;

procedure TForm1.CopyDataSourceClick(Sender: TObject);
var
Stream1: TBlobStream;
Stream2: TStream;
blobType : TBlobType;
begin
blobType := myBlobField.BlobType;
DBImage2.DataField := 'Pictures';
Stream1 := TBlobStream.Create(myBlobField, bmRead);
try
CDS2.Edit;
{ This is a different way to create a blob stream. }
Stream2 := CDS2.CreateBlobStream(CDS2.FieldByName('Pictures') , bmReadWrite);
try
Stream2.CopyFrom(Stream1, Stream1.Size);
// CDS2.Post;
// CDS2.Active := True;
finally
Stream2.Free;
end;
finally
Stream1.Free;
end;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
I : Integer;
S : String;
ft : TFieldType;
myString: String;
begin
// These properties can also be set statically at design time.
Table1.DatabaseName := 'DBDEMOS';
Table1.TableName := 'BioLife.DB';
DataSource1.DataSet := Table1;
DBGrid1.DataSource := DataSource1;
Table1.Active := True; // Do this last
myBlobField := nil;
for I := 0 to Table1.FieldCount - 1 do
begin
S := Table1.Fields[I].FieldName;
ft := Table1.Fields[I].DataType;
case ft of
ftFloat: myString := 'float';
ftBoolean: myString := 'boolean';
ftInteger: myString := 'integer';
ftString: myString := 'string';
ftCurrency: myString := 'currency';
ftBlob:
begin
myString := 'blob';
if (Table1.Fields[I] is TBlobField) then
myBlobField := TBlobField(Table1.Fields[I]);
end;
ftSmallint: myString := 'smallint';
ftTime: myString := 'time';
ftDate: myString := 'date';
ftDateTime: myString := 'datetime';
ftTypedBinary: myString := 'typedBinary';
ftMemo: myString := 'memo';
ftGraphic: myString := 'graphic';
ftAutoInc: myString := 'autoinc';
else myString := 'unknown';
end;
ListBox1.Items.Add('Field ' + S + ' is of type: ' + myString);
end;
if (myBlobField <> nil) then
begin
with CDS2 do
begin
with FieldDefs.AddFieldDef do
begin
DataType := ftInteger;
Name := 'Field1';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftBlob;
Size := 10;
Name := 'Pictures';
end;
with IndexDefs.AddIndexDef do
begin
Fields := 'Field1';
Name := 'IntIndex';
end;
CreateDataSet;
// DBMemo2.DataField := 'Remarks';
end;
end;
end;