Configurable Plugin in 10.x multi line string control?

Instead of control types, you now specify a template. The platform includes a list of available configurable templates that are listed within Widget and Theme Studio API Documentation under "Configuration Property Templates".  The equivalent to the multilinestringcontrol is the template "string" (which is also the default for string inputs) with configuration for rows (> 1 makes it multiline) and columns.

Widgets and themes can also reference script files as template names (see the dynamic configuration documentation for more details). As a plugin developer, you can implement ITemplateableConfigurablePlugin to define your own templates that can be used within your plugin.

Templates are lighter weight and remove the dependency on ASP.Net Server Controls. The default set of templates is much more feature rich than the older property control implementations.

Thanks Ben...  How do I configure this for rows > 1?

So render a box like this in a configurable plugin.

The extended options are assigned via the Attributes dictionary on the Property.

I'm not seeing An Attributes dictionary on the Intellisense popup on the Property object.

I do see an Options property that is a NameValueCollection

                // TODO:  Add MultilineStringControl type here.
                // Assemblies
                var assemblies = new Property {
                    Id = BadgeConstants.ADDITIONAL_ASSEMBLIES,
                    LabelText = "Additional Assemblies.",
                    DataType = "String",
                    OrderNumber = 1,
                    DefaultValue = "",
                    DescriptionText = "A csv string containing assembly names that implement various badging interfaces such as IRequirementType or IGamificationMetric. (ex: Microsoft.Assembly.dll)",
                    Template = "string",  
                     
                };
                assemblies.Options.Add("rows", "10");

                // TODO:  Add MultilineStringControl type here.
                // Assemblies
                var assemblies = new Property {
                    Id = BadgeConstants.ADDITIONAL_ASSEMBLIES,
                    LabelText = "Additional Assemblies.",
                    DataType = "String",
                    OrderNumber = 1,
                    DefaultValue = "",
                    DescriptionText = "A csv string containing assembly names that implement various badging interfaces such as IRequirementType or IGamificationMetric. (ex: Microsoft.Assembly.dll)",
                    Template = "string",  
                     
                };
                assemblies.Options.Add("rows", "10");

Sorry. Yes, Options is correct.