TdxReportParameters Class

A collection of report parameters.

Declaration

TdxReportParameters = class(
    TdxBackendCustomParameters<TdxReportParameter>
)

Remarks

Report parameters are dynamic values that can replace constants in a report query, filter criteria, expressions, and calculated fields. The TdxReportParameters class implements a collection of report parameters.

The TdxReportParameters collection is automatically populated and updated from the current report template definition. The list of parameter is read-only. You can only access and modify parameter properties.

Note

If the list of parameters changes within the report template definition, the collection is updated automatically the next time you access it in code.

Main API Members

The list below outlines key members of the TdxReportParameters class. These members allow you to access and modify parameters in a report:

Count: Returns the number of parameters stored in the collection.
FindParam: Returns the stored parameter with the specified name or returns nil / nullptr if the collection does not contain the target parameter. Use this method to safely search for a parameter that may not exist.
Items: Returns the stored parameter by its index in the collection.
ParamByName: Returns the stored parameter with the specified name or raises an exception if the collection does not contain the target parameter.
Note
You can omit ParamByName and use only the parameter name in square brackets (for example, dxControl1.Parameters['ParameterName'] instead of dxControl1.Parameters.ParamByName['ParameterName']).

uses
  dxReport.Control,      // Declares the TdxReportControl class
  dxReport.Parameters,   // Declares the TdxReportParameter class
  dxMessageDialog,       // Declares the TdxMessageDialogForm class
  System.StrUtils;       // Provides advanced string management routines

procedure TForm1.cxButton1Click(Sender: TObject);
var
  AList: TStringList;
  AParameter: TdxReportParameter;
begin
  // Create a TStringList instance
  AList := TStringList.Create;
  try
    // Iterate through report parameters
    for AParameter in dxReportControl1.Parameters do
      AList.Add(Format('- %s', [
        // Use the parameter Name if Description is missing
        IfThen(AParameter.Description <> '', AParameter.Description, AParameter.Name)
      ]));
    // Display the parameter list or a notification message if the list is empty
    if AList.Count > 0 then
      dxShowMessage(AList.Text)
    else
      dxShowMessage('The report has no parameters.');
  finally
    AList.Free;
  end;
end;

#include "dxReport.Control.hpp"      // Declares the TdxReportControl class
#include "dxReport.Parameters.hpp"   // Declares the TdxReportParameter class
#include "dxMessageDialog.hpp"       // Declares the TdxMessageDialogForm class

// Add the following linker directives to the corresponding CPP source file:
#pragma link "dxReport.Control"   // Required to use dxReport.Control.hpp declarations

void __fastcall TForm1::cxButton1Click(TObject* Sender) {
  TStringList* AList = new TStringList();
  try {
    // Iterate through report parameters
    for (int i = 0; i < dxReportControl1->Parameters->Count; i++) {
      TdxReportParameter* AParameter = dxReportControl1->Parameters->Items[i];
      UnicodeString ALabel;
      // Use the parameter Name if Description is missing
      if (AParameter->Description.IsEmpty())
        ALabel = AParameter->Name;
      else
        ALabel = AParameter->Description;
      AList->Add(Format(L"- %s", ARRAYOFCONST((ALabel))));
    }
    // Display the parameter list or a notification message if the list is empty
    if (AList->Count > 0)
      dxShowMessage(AList->Text);
    else
      dxShowMessage(L"The report has no parameters.");
  }
  __finally {
    delete AList;
  }
}