public class Global : System.Web.HttpApplication
{


    protected void Application_Start(object sender, EventArgs e)
    {
        Bootstrapper.Bootstrapped += Bootstrapper_Bootstrapped;
    }

    private void Bootstrapper_Bootstrapped(object sender, EventArgs e)
    {
        ObjectFactory.Container.RegisterType<FormsConnectorDefinitionsExtender, CrmWorkflowConnectorExtender>("CrmWorkflowConnectorExtender");
        ObjectFactory.Container.RegisterType<IModuleConnectionStatus, CrmWorkflowConnectorExtenderConnectionStatus>(typeof(CrmWorkflowConnectorExtenderConnectionStatus).FullName, new ContainerControlledLifetimeManager());
    }

}

public class CrmWorkflowConnectorExtender : FormsConnectorDefinitionsExtender
{
    public override int Ordinal
    {
        get { return 1; }
    }


    public override string ConnectorName => "CrmConnectorModule";

    public override string ConnectorTitle => "CRM Connector";

    public override string SectionTitle => "Send data to dynamics CRM";

    public override void AddConnectorSettings(ConfigElementDictionary<string, FieldDefinitionElement> sectionFields)
    {
        var CRMWorkflowField = new ChoiceFieldElement(sectionFields)
        {
            Title = "Select CRM Workflow",
            FieldName = "CRMWorkflowSelection",
            DataFieldName = "CRMWorkflowSelection",
            DisplayMode = FieldDisplayMode.Write,
            FieldType = typeof(Telerik.Sitefinity.Web.UI.Fields.ChoiceField),
            RenderChoiceAs = RenderChoicesAs.DropDown,
            ID = "CRMWorkflowSelectionID"
        };

        //foreach (var workflow in GetWorkflowDefinitions())
        //{
        //    var choice = new ChoiceElement(CRMWorkflowField.ChoicesConfig)
        //    {
        //        Text = workflow.WorkflowName,
        //        Value = workflow.WorkflowName
        //    };
        //    CRMWorkflowField.ChoicesConfig.Add(choice);
        //}

        var mychoices = new List<ChoiceDefinition>();
        mychoices.Add(new ChoiceDefinition()
        {
            Text = "MVCOnly",
            ResourceClassId = typeof(FormsResources).Name,
            Value = "0"
        });

        mychoices.Add(new ChoiceDefinition()
        {
            Text = "WebFormsOnly",
            ResourceClassId = typeof(FormsResources).Name,
            Value = "1"
        });

        CRMWorkflowField.Choices.AddRange(mychoices);
        sectionFields.Add(CRMWorkflowField.ID, CRMWorkflowField);
    }

    private IEnumerable<WorkflowDefinitionDto> GetWorkflowDefinitions()
    {
        var manager = DynamicModuleManager.GetManager();
        var type = TypeResolutionService.ResolveType("Telerik.Sitefinity.DynamicTypes.Model.CrmWorkflows.WorkflowDefinition");

        IEnumerable<WorkflowDefinitionDto> workflows = manager.GetDataItems(type)
            .Where(w => w.Status == ContentLifecycleStatus.Live && w.Visible)
            .Select(w => new WorkflowDefinitionDto
            {
                WorkflowName = w.GetValue<string>("WorkflowName")
            });

        return workflows;
    }

    private class WorkflowDefinitionDto
    {
        public string WorkflowName { get; set; }
    }
}

public class CrmWorkflowConnectorExtenderConnectionStatus : IModuleConnectionStatus
{
    public string ModuleName => "CrmConnector.CrmConnectorModule";

    public void ExecuteIfConfigured(Action action)
    {
        // Add code to check that the connector is connected
        // ex. if (this.connector.IsConnected())
        if (action != null)
            action();
    }

    // IMPORTANT: This callback is not invoked as part of Forms connectors. You still need to implement it, as it is used elsewhere.
    public void ExecuteIfNotConfigured(Action action)
    {
        // Add code to check that the connector is not configured
        // ex. if (!this.connector.IsConnected())
        if (action != null)
            action();
    }
}

Type : System.ArgumentException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Message : ‹‹‹An item with the same key has already been added.›››
Source : mscorlib
Help link : 
ParamName : 
Data : ‹‹‹System.Collections.ListDictionaryInternal›››
TargetSite : ‹‹‹Void ThrowArgumentException(System.ExceptionResource)›››
HResult : ‹‹‹-2147024809›››
Stack Trace :    at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at Telerik.Sitefinity.Web.Api.Strategies.Forms.Connectors.FormConnectorService.ResolveUIField(List`1 fields, FieldDefinitionElement fieldDefinitionElement, ConnectorDataMappingExtender mappingExtender, SectionFieldWrapper predecessorField)
   at Telerik.Sitefinity.Web.Api.Strategies.Forms.Connectors.FormConnectorService.AdjustFields(List`1 fields, SectionFieldWrapper predecessorField)