This blog provides code snippets that demonstrate how to use EC Expression with properties:
Expressions currently work with Primitive properties. They do not support Struct or Array type of properties.Below steps explain how to use Managed and Native EC Expression API’s with EC Property:
- Set EC Expression in item type property definition.
- Set EC Expression Failure value in item type property definition.
- Get EC Expression from item type property definition.
- Get EC Expression Failure value from item type property definition.
- Verify input EC Expression is valid or not.
Sample EC Schema
Following is the EC Schema used to perform set/get EC Expression operations onto EC Properties:
<?xml version="1.0" encoding="utf-8"?><ECSchema schemaName="PropertyTypes" nameSpacePrefix="pt" version="1.0" description="For testing properties" xmlns="http://www.bentley.com/schemas/Bentley.ECXML.2.0"><ECClass typeName="PropertiesClass" isDomainClass="True"><ECProperty propertyName="StringProperty" typeName="string" readOnly="True"><ECCustomAttributes><CalculatedECPropertySpecification xmlns="Bentley_Standard_CustomAttributes.01.13"><ECExpression>this.GetElement().ElementDescription</ECExpression><FailureValue>Failed String Expression</FailureValue><IsDefaultValueOnly>False</IsDefaultValueOnly><RequiredSymbolSets><string>System.Math</string><string>System.Path</string><string>System.String</string><string>Items</string><string>LookUp</string></RequiredSymbolSets><EnforceUnits>False</EnforceUnits></CalculatedECPropertySpecification></ECCustomAttributes></ECProperty></ECClass></ECSchema>
API’s to work with EC Expression
Following are the APIs used to set EC Expression in item type property definition:
- Native API to set EC Expression
auto& dgnfile = *GetDgnModelP()->GetDgnFileP(); ItemTypeLibraryPtr lib = ItemTypeLibrary::Create(L"PropertyTypes", dgnfile); ItemTypeP itp1 = lib->AddItemType(L"PropertiesClass"); CustomPropertyP prop1 = itp1->AddProperty(L"StringProperty"); prop1->SetType(CustomProperty::Type::String); prop1->SetExpression(L"this.GetElement().ElementDescription"); lib->Write();
- Managed API to set EC Expression
ItemTypeLibrary itLibrary = ItemTypeLibrary.Create("PropertyTypes", GetDgnFile());
ItemType itp = itLibrary.AddItemType ("PropertiesClass");
CustomProperty property = itp.AddProperty("StringProperty");
property.Type = CustomProperty.TypeKind.String;
property.SetExpression(“this.GetElement().ElementDescription”);
itLibrary.Write();
- VBA COM API to set EC Expression,Failure Value
Function CreateItemTypeLibrary(sLibName As String) As ItemTypeLibrary
Dim oItem As ItemType
Dim oItemProp As ItemTypeProperty
Dim oItemLibs As ItemTypeLibraries
Dim sMessage As String'Create ItemType Library
Set oItemLibs = New ItemTypeLibraries
Set CreateItemTypeLibrary = oItemLibs.CreateLib(sLibName, False)
If CreateItemTypeLibrary Is Nothing Then
MsgBox("ItemTypeLibrary with name TestLibrary already exist")
Else 'Create first ItemType
Set oItem = CreateItemTypeLibrary.AddItemType("FirstItemType")'Calculated property
Set oItemProp = oItem.AddProperty("StringProperty", ItemPropertyTypeString)
Success = oItemProp.SetExpression("10+20", "Failed String Expression", sMessage)
If Not sMessage = "" Then
MsgBox(sMessage)
End If
CreateItemTypeLibrary.Write
End If
End FunctionFollowing are the APIs used to set EC Expression Failure value in item type property definition:
- Native API to set EC Expression Failure value
auto& dgnfile = *GetDgnModelP()->GetDgnFileP(); ItemTypeLibraryPtr lib = ItemTypeLibrary::Create(L"PropertyTypes", dgnfile); ItemTypeP itp1 = lib->AddItemType(L"PropertiesClass"); CustomPropertyP prop1 = itp1->AddProperty(L"StringProperty"); prop1->SetType(CustomProperty::Type::String); prop1->SetExpression(L"this.GetElement().ElementDescription",L"Failed String Expression"); lib->Write();
- Managed API to set EC Expression Failure value
ItemTypeLibrary itLibrary = ItemTypeLibrary.Create("PropertyTypes", GetDgnFile());
ItemType itp = itLibrary.AddItemType ("PropertiesClass");
CustomProperty property = itp.AddProperty("StringProperty");
property.Type = CustomProperty.TypeKind.String;
property.SetExpression(“this.GetElement().ElementDescription”, "Failed String Expression");
itLibrary.Write();Following are the APIs used to get EC Expression from item type property definition:
- Native API to get EC Expression
auto& dgnfile = *GetDgnModelP()->GetDgnFileP(); ItemTypeLibraryPtr lib = ItemTypeLibrary::Create(L"PropertyTypes", dgnfile); ItemTypeP itp1 = lib->AddItemType(L"PropertiesClass"); CustomPropertyP prop1 = itp1->AddProperty(L"StringProperty"); prop1->SetType(CustomProperty::Type::String); prop1->SetExpression(L"this.GetElement().ElementDescription"); lib->Write(); ECValue value; prop1->GetExpression(value); wprintf (L"Expression=", value.ToString().c_str());
- Managed API to get EC Expression
ItemTypeLibrary itLibrary = ItemTypeLibrary.Create("PropertyTypes", GetDgnFile());
ItemType itp = itLibrary.AddItemType ("PropertiesClass");
CustomProperty property = itp.AddProperty("StringProperty");
property.Type = CustomProperty.TypeKind.String;
property.SetExpression((“this.GetElement().ElementDescription”);
itLibrary.Write();
Console.WriteLine("Expression=", property.Expression);- VBA COM API to get EC Expression
Set CreateItemTypeLibrary = oItemLibs.CreateLib(sLibName, False)
Set oItem = CreateItemTypeLibrary.AddItemType("FirstItemType")
Set oItemProp = oItem.AddProperty("StringProperty", ItemPropertyTypeString)
Success = oItemProp.SetExpression("10+20", "Failed String Expression", sMessage)
CreateItemTypeLibrary.Write
Debug.Print "Expression= " & itemTypeProp.GetExpression & vbNewLine; Following are the APIs used to get EC Expression Failure value from item type property definition:
- Native API to get EC Expression Failure value
auto& dgnfile = *GetDgnModelP()->GetDgnFileP(); ItemTypeLibraryPtr lib = ItemTypeLibrary::Create(L"PropertyTypes", dgnfile); ItemTypeP itp1 = lib->AddItemType(L"PropertiesClass"); CustomPropertyP prop1 = itp1->AddProperty(L"StringProperty"); prop1->SetType(CustomProperty::Type::String); prop1->SetExpression(L"this.GetElement().ElementDescription",L"Failed String Expression"); lib->Write(); ECValue value; prop1->GetExpressionFailureValue (value); wprintf (L"ExpressionFaluireValue=", value.ToString().c_str());
- Managed API to get EC Expression Failure value
ItemTypeLibrary itLibrary = ItemTypeLibrary.Create("PropertyTypes", GetDgnFile());
ItemType itp = itLibrary.AddItemType ("PropertiesClass");
CustomProperty property = itp.AddProperty("StringProperty");
property.Type = CustomProperty.TypeKind.String;
property.SetExpression("this.GetElement().ElementDescription", "Failed String Expression");
itLibrary.Write();
Console.WriteLine("Expression=", property.ExpressionFailureValue);- VBA COM API to get EC Expression Failure value
Set CreateItemTypeLibrary = oItemLibs.CreateLib(sLibName, False)
Set oItem = CreateItemTypeLibrary.AddItemType("FirstItemType")
Set oItemProp = oItem.AddProperty("StringProperty", ItemPropertyTypeString)
Success = oItemProp.SetExpression("10+20", "Failed String Expression", sMessage)
CreateItemTypeLibrary.Write
failureValue = itemTypeProp.GetExpressionFailureValue
Debug.Print "Calulated property failure value = " & failureValue & vbNewLine; Following are the APIs used to verify input EC Expression is valid or not:
- Native API to verify EC Expression is valid or not
auto& dgnfile = *GetDgnModelP()->GetDgnFileP();
ItemTypeLibraryPtr lib = ItemTypeLibrary::Create(L"PropertyTypes", dgnfile);
ItemTypeP itp1 = lib->AddItemType(L"PropertiesClass");
CustomPropertyP prop1 = itp1->AddProperty(L"StringProperty");
prop1->SetType(CustomProperty::Type::String);
WCharCP message = L"";
WCharCP expression = L"1**2";
if (prop1->isValidExpression (expression, message))
prop1->SetExpression (expression, L"Failed String Expression");
else
wprintf (message);
lib->Write();- Managed API to verify EC Expression is valid or not
ItemTypeLibrary itLibrary = ItemTypeLibrary.Create("PropertyTypes", GetDgnFile());
ItemType itp = itLibrary.AddItemType ("PropertiesClass");
CustomProperty property = itp.AddProperty("StringProperty");
property.Type = CustomProperty.TypeKind.String;
property.SetExpression(expression, "Failed String Expression");
itLibrary.Write();
String expression = "1**2;
String message = "";
if (property1.isValidExpression(expression,true,message))
property1.SetExpression(expression);
else
Console.WriteLine(message);- VBA COM API to get EC Expression Failure value
Set CreateItemTypeLibrary = oItemLibs.CreateLib(sLibName, False)
Set oItem = CreateItemTypeLibrary.AddItemType("FirstItemType")
Set oItemProp = oItem.AddProperty("StringProperty", ItemPropertyTypeString)
Success = oItemProp.SetExpression("10**20", "Failed String Expression", sMessage)
If Not sMessage = "" Then
MsgBox(sMessage)
End If
CreateItemTypeLibrary.Write
