我用SQL搜尋出來的資料用DBGrid顯示，可是有些欄位出現MEMO，這是什麼原因？

因為dbgrid不支援 LOB 屬性的欄位

===================引 用 egghead253 文 章===================
我用SQL搜尋出來的資料用DBGrid顯示，可是有些欄位出現MEMO，這是什麼原因？

我用Access匯入的，那有辨法可以呼叫出來嗎？
===================引 用 GrandRURU 文 章===================
因為dbgrid不支援 LOB 屬性的欄位

===================引 用 egghead253 文 章===================
我用SQL搜尋出來的資料用DBGrid顯示，可是有些欄位出現MEMO，這是什麼原因？

出處：使用tdbgrid如何使memo欄位出現內容

[code delphi]
{
Uploader: Helmut Dollinger
Company: Reference: N/A

Question/Problem/Abstract:

By default the DBGrid Control of the VCL can't display memo fields.
Here is a solution...
Answer:

The problem can be solved with the OnDrawDataCell event of the DBGrid.
}
procedure TForm1.DBGrid1DrawDataCell(Sender: TObject; const
Rect: TRect; Field: TField; State:
TGridDrawState);
var
P: array [0..50] of char; {array size is number of
characters needed}
bs: TBlobStream; {from the memo field}
hStr: String;
begin
if Field is TMemoField then
begin
with (Sender as TDBGrid).Canvas do
begin {Table1Notes is the TMemoField}
bs := TBlobStream.Create(Table1Notes, bmRead);
FillChar(P,SizeOf(P),#0); {terminate the null string}
bs.Read(P, 50); {read 50 chars from memo into blobStream}
bs.Free;
hStr := StrPas(P);
while Pos(#13, hStr) > 0 do {remove carriage returns and}
hStr[Pos(#13, hStr)] := ' ';
while Pos(#10, hStr) > 0 do {line feeds}
S[Pos(#10, hStr)] := ' ';

FillRect(Rect); {clear the cell}
TextOut(Rect.Left, Rect.Top, hStr); {fill cell with memo
data}
end;
end;
end;

{Note: before running create a TMemoField object for the
memo field by double clicking on the TTable component
and adding the memo field.}
[/code]

編輯記錄

我試著改bcb有兩個地方不曉得怎麼改，請指導一下，謝謝
[code cpp]
void __fastcall TForm1::DBGrid1DrawDataCell(TObject *Sender,
const TRect &Rect, TField *Field, TGridDrawState State)
{
char P[50];
TBlobStream *bs;
AnsiString hStr;
//if Field is TMemoField then //這行不知道怎麼改
if (Field->DataType == ftMemo)
{
TCanvas *ACanvas = ((TDBGrid *)Sender)->Canvas;
bs = new TBlobStream(Table1Notes, bmRead); //這行不知道怎麼改，一直error
//bs = new TBlobStream((TMemoField *)Field, bmRead);
//raised exception class EInvalidCast with message 'Invalid class typecast'
memset(P,char(0x0),sizeof(P));
bs->Read(P, 50);
bs->Free();
hStr = StrPas(P);
while (hStr.Pos(char(0x13)) > 0)
hStr[hStr.Pos(char(0x13))] = ' ';
while (hStr.Pos(char(0x10)) > 0)
hStr[hStr.Pos(char(0x10))] = ' ';
ACanvas->FillRect(Rect);
ACanvas->TextOut(Rect.Left, Rect.Top, hStr);
}
}
[/code]

另外有找到一篇DBGrid如何顯示text型態欄位資料
沒使用TBlobStream效果好像也差不多
[code cpp]
void __fastcall TForm1::DBGrid1DrawColumnCell(TObject *Sender,
const TRect &Rect, int DataCol, TColumn *Column,
TGridDrawState State)
{
TField *F;
TCanvas *ACanvas;
F=Column->Field;
if (!(F->DataType == ftMemo ||
F->DataType == ftFmtMemo )) return;
ACanvas = ((TDBGrid *)Sender)->Canvas;
ACanvas->TextRect(Rect,Rect.Left,Rect.Top,F->AsString);
}
[/code]

編輯記錄

===================引 用 senso 文 章===================
我試著改bcb有兩個地方不曉得怎麼改，請指導一下，謝謝
[code cpp]
void __fastcall TForm1::DBGrid1DrawDataCell(TObject *Sender,
const TRect &Rect, TField *Field, TGridDrawState State)
{
char P[50];
TBlobStream *bs;
AnsiString hStr;
// if (Field->ClassNameIs(TMemoField)) ↓ 試試看
//if Field is TMemoField then //這行不知道怎麼改
if (Field->DataType == ftMemo)
{
TCanvas *ACanvas = ((TDBGrid *)Sender)->Canvas;
// #include ＜DBTables.hpp＞ 試試看
bs = new TBlobStream(Table1Notes, bmRead); //這行不知道怎麼改，一直error
}
}
[/code]

編輯記錄

謝謝指導!

原來是ClassName...汗
我有#include 不然編輯期間就error了
還是搞不懂怎麼new TBlobStream，只好參考別的方式來寫
關於DBGrid顯示memo型態資料問題
另外
在 DBGrid 內顯示 Memo 內容之後的欄位格子會有殘影

[code cpp]
void __fastcall TForm1::DBGrid1DrawDataCell(TObject *Sender,
const TRect &Rect, TField *Field, TGridDrawState State)
{
char P[50];
TBlobStream *bs;
//或用TStream *bs;
AnsiString hStr=Field->AsString;
if (Field->ClassNameIs("TMemoField"))
//或 if (Field->ClassNameIs(Field->ClassType(),"TMemoField"))
//其實一樣, ClassNameIs(const AnsiString string)就是call ClassNameIs(TClass cls, const AnsiString string)
{
TCanvas *ACanvas = ((TDBGrid *)Sender)->Canvas;
//bs = new TBlobStream(Table1Notes, bmRead); //這行不知道怎麼改，一直error
//bs = new TBlobStream((TMemoField *)Field, bmRead);
//raised exception class EInvalidCast with message 'Invalid class typecast'

bs = (TBlobStream *)((TDBGrid *)Sender)->DataSource->DataSet->CreateBlobStream(Field,bmRead);
//或用TStream
//bs = ((TDBGrid *)Sender)->DataSource->DataSet->CreateBlobStream(Field,bmRead);
memset(P,char(0x0),sizeof(P));
bs->Read(P, 50);
bs->Free();
hStr = StrPas(P);
while (hStr.Pos(char(0x13)) > 0)
hStr[hStr.Pos(char(0x13))] = ' ';
while (hStr.Pos(char(0x10)) > 0)
hStr[hStr.Pos(char(0x10))] = ' ';
ACanvas->FillRect(Rect);
//ACanvas->TextOut(Rect.Left, Rect.Top, hStr);
//改用TextRect
ACanvas->TextRect(Rect,Rect.Left,Rect.Top,hStr);
}
}
[/code]

編輯記錄

 那個寫法是給bde的，如果你是用ado的話，有另一種寫法。

請參考CSDN這篇
将图片存入SQL数据库的image字段，使用流类，出错，怎么解决？

我剛好是用ADO來試...  0rz
改TADOBlobStream就沒跳error了
謝謝~

===================引 用 GrandRURU 文 章===================
那個寫法是給bde的，如果你是用ado的話，有另一種寫法。

請參考CSDN這篇
将图片存入SQL数据库的image字段，使用流类，出错，怎么解决？