如何使用活动绑定将blob字段绑定到TImage控件？

Question

我正在使用Delphi XE2编写一个VCL win32应用程序。Delphi XE2支持活动绑定。我将示例Biolife.xml加载到一个TClientDataSet实例中。

我可以将TEdit控件绑定到dataset的字符串字段:物种名称：

object BindLinkEdit11: TBindLink
  Category = 'Links'
  SourceMemberName = 'Species Name'
  ControlComponent = Edit1
  SourceComponent = BindScopeDB1
  ParseExpressions = <>
  FormatExpressions = <
    item
      ControlExpression = 'Text'
      SourceExpression = 'DisplayText'
    end>
  ClearExpressions = <>
end

然后，我尝试将图形字段绑定到TImage控件：

object BindLinkImage11: TBindLink
  Category = 'Links'
  SourceMemberName = 'Graphic'
  ControlComponent = Image1
  SourceComponent = BindScopeDB1
  ParseExpressions = <>
  FormatExpressions = <
    item
      ControlExpression = 'Picture'
      SourceExpression = 'Value'
    end>
  ClearExpressions = <>
end

显然，它不起作用。这样做有可能吗？

Answer 1

看一看BindLinkVCLProject演示项目。这里还显示了图像的绑定，所以我猜您需要这样做( SourceExpression中的Self表示一个blob字段)：

object BindLinkImageHandler: TBindLink
  Category = 'Links'
  SourceMemberName = 'Graphic'
  ControlComponent = Image1
  SourceComponent = BindScopeDB1
  ParseExpressions = <
    item
      ControlExpression = 'Picture'
      SourceExpression = 'Self'
    end>
  FormatExpressions = <
    item
      ControlExpression = 'Picture'
      SourceExpression = 'Self'
    end>
  ClearExpressions = <
    item
      ControlExpression = 'Picture'
      SourceExpression = 'nil'
    end>
end