Delphi TClientDataSet定位问题

发布于 2024-12-18 08:45:01 字数 874 浏览 3 评论 0原文

我正在使用 Delphi7、MS Vista 和 Devart's dbExpress 驱动程序（版本 4.70）。我删除了一个 TSQLConnection、一个 TSQLTable (tabA)、一个 TDataSetProvider、一个 TClientDataSet(cdsA)、一个DataSource 和一个DBGrid。

我通过图形设计工具进行了所有设置。一切正常，当我打开 cdsA 时，我可以看到网格中的所有数据。这是我的代码：

procedure TForm1.Button1Click(Sender: TObject);
var
  fields, values: string;
begin
  cdsA.Close;
  cdsA.Open;
  fields := 'fielda;fieldb';
  values := Edit1.Text+';'+Edit2.Text;
  cdsA.SetKey;
  cdsA.Locate(fields, values, [loCaseInsensitive]);
end;

fieldA 和 fieldB 存在于表中，并且也在 cdsA.Fields 中定义。当我执行此代码时，Locate 指令生成异常 EVariantInvalidArgError ... Invalid argument。我想知道出了什么问题。 TIA。

弗朗西斯科

原文

I'm using Delphi7, MS Vista and Devart's dbExpress drivers (version 4.70). I drop a TSQLConnection, a TSQLTable (tabA), a TDataSetProvider, a TClientDataSet(cdsA), a DataSource and a DBGrid.

I made all the settings via graphical design tool. Everything works fine, as I open cdsA, I can see all the data in the Grid. Here is my code:

procedure TForm1.Button1Click(Sender: TObject);
var
  fields, values: string;
begin
  cdsA.Close;
  cdsA.Open;
  fields := 'fielda;fieldb';
  values := Edit1.Text+';'+Edit2.Text;
  cdsA.SetKey;
  cdsA.Locate(fields, values, [loCaseInsensitive]);
end;

fieldA and fieldB exists in table and are defined in cdsA.Fields too. When I execute this code the Locate instruction generate exception EVariantInvalidArgError ... Invalid argument. I'm wondering what's wrong. TIA.

Francesco

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合久必婚 2024-12-25 08:45:01

你的代码是错误的。 :)

procedure TForm1.Button1Click(Sender: TObject);
var
  fields, values: string;
begin
  // Closing the CDS and opening it every time is foolish. Just
  // open it if it's not already open.
  if not cdsA.Active then
    cdsA.Open;

  // List of column names. Since column (field) names are always
  // strings, can just use semicolon-separated values
  fields := 'fielda;fieldb'; 

  // Values for columns. Since these could be any type, you can't
  // simply use semicolon-separated strings. You have to pass an
  // array of Variants. The easiest way is to just create it and
  // populate it, and let reference counting release it when it's
  // out of scope
  values := VarArrayOf([Edit1.Text, Edit2.Text]);  

  // No call to SetKey here. SetKey is used with FindKey, not Locate
  cdsA.Locate(fields, values, [loCaseInsensitive]);
end;

Your code is wrong. :)

procedure TForm1.Button1Click(Sender: TObject);
var
  fields, values: string;
begin
  // Closing the CDS and opening it every time is foolish. Just
  // open it if it's not already open.
  if not cdsA.Active then
    cdsA.Open;

  // List of column names. Since column (field) names are always
  // strings, can just use semicolon-separated values
  fields := 'fielda;fieldb'; 

  // Values for columns. Since these could be any type, you can't
  // simply use semicolon-separated strings. You have to pass an
  // array of Variants. The easiest way is to just create it and
  // populate it, and let reference counting release it when it's
  // out of scope
  values := VarArrayOf([Edit1.Text, Edit2.Text]);  

  // No call to SetKey here. SetKey is used with FindKey, not Locate
  cdsA.Locate(fields, values, [loCaseInsensitive]);
end;

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