TdxBackendCustomParameter Class

The base class for parameters used in TdxDashboard/TdxDashboardControl and TdxReport/TdxReportControl components.

Declaration

TdxBackendCustomParameter = class abstract(TCollectionItem)

Remarks

Parameters allow you to apply dynamic filters to source data for TdxDashboard/TdxDashboardControl and TdxReport/TdxReportControl components.

Main API Members

The list below outlines key members of the TdxBackendCustomParameter class. These members allow you to configure data field parameters in backend client components.

AllowNull

Specifies whether Null can be assigned as the parameter value.

DataType

Returns the parameter data type.

Description

Returns the parameter label displayed in the UI.

Enabled

Specifies if users can change the parameter value in the UI.

IsMultiValueParameter

Indicates if the parameter has multiple values.

IsRangeParameter

Indicates whether the parameter defines a date/time range.

Name

Returns the unique parameter identifier.

Value | Values

Specify the default parameter value.

Visible

Specifies whether the parameter editor is visible in the UI.

Indirect TdxBackendCustomParameter References

The following public API members reference the TdxBackendCustomParameter class as terminal descendant instances:

TdxBackendCustomParameters.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.

TdxBackendCustomParameters.Items

Returns the stored parameter by its index in the collection.

TdxBackendCustomParameters.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']).

Terminal TdxBackendCustomParameter Class Descendants

Do not use the TdxBackendCustomParameter class directly. Use the following descendants instead:

TdxDashboardParameter

A dashboard parameter.

TdxReportParameter

A report parameter.

Code Examples

The following code snippets display all parameter labels or a unique identifier where a label is missing. They perform the same operation but use component-specific APIs to access properties.

List Report Parameter Labels

Delphi

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;

C++

#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;
  }
}

List Dashboard Parameter Labels

Delphi

uses
  dxDashboard.Control,      // Declares the TdxDashboardControl class
  dxDashboard.Parameters,   // Declares the TdxDashboardParameter class
  dxMessageDialog,          // Declares the TdxMessageDialogForm class
  System.StrUtils;          // Provides advanced string management routines

procedure TForm1.cxButton1Click(Sender: TObject);
var
  AList: TStringList;
  AParameter: TdxDashboardParameter;
begin
  // Create a TStringList instance
  AList := TStringList.Create;
  try
    // Iterate through dashboard parameters
    for AParameter in dxDashboardControl1.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 dashboard has no parameters.');
  finally
    AList.Free;
  end;
end;

C++

#include "dxDashboard.Control.hpp"      // Declares the TdxDashboardControl class
#include "dxDashboard.Parameters.hpp"   // Declares the TdxDashboardParameter class
#include "dxMessageDialog.hpp"          // Declares the TdxMessageDialogForm class

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

void __fastcall TForm1::cxButton1Click(TObject* Sender) {
  TStringList* AList = new TStringList();
  try {
    // Iterate through dashboard parameters
    for (int i = 0; i < dxDashboardControl1->Parameters->Count; i++) {
      TdxDashboardParameter* AParameter = dxDashboardControl1->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 dashboard has no parameters.");
  }
  __finally {
    delete AList;
  }
}

Inheritance

TObject

TPersistent

TCollectionItem

TdxBackendCustomParameter