Working proof of concept for FluentForms.

Maui.FluentForms/Builders/FormFieldBuilder.cs

@@ -6,9 +6,8 @@
 
 namespace Maui.FluentForms.Builders;
 
-internal class FormFieldBuilder<TModel, TProperty> : IFormFieldBuilder<TModel>,
+public class FormFieldBuilder<TModel, TProperty> : IFormFieldBuilder<TModel>,
     ICheckBoxFormFieldBuilder<TModel>,
-    ICustomTemplateFormFieldBuilder<TModel>,
     IDatePickerFormFieldBuilder<TModel>,
     IEditorFormFieldBuilder<TModel>,
     IEntryFormFieldBuilder<TModel>,
@@ -18,184 +17,164 @@ internal class FormFieldBuilder<TModel, TProperty> : IFormFieldBuilder<TModel>,
     ITimePickerFormFieldBuilder<TModel>
 
 {
-    private readonly Expression<Func<TModel, TProperty>> expression;
-
-    private string controlTemplateName;
-
-    private IFormFieldConfiguration formFieldConfiguration;
-    private FormFieldLayoutConfiguration layoutConfiguration;
+    protected Expression<Func<TModel, TProperty>> Expression { get; init; }
+    protected string FormFieldTemplateName { get; set; }
+    protected IFormFieldConfiguration FormFieldConfiguration { get; set; }
+    protected FormFieldLayoutConfiguration LayoutConfiguration { get; set; } = new FormFieldLayoutConfiguration();
 
     public FormFieldBuilder(Expression<Func<TModel, TProperty>> expression)
     {
-        this.expression = expression;
+        this.Expression = expression;
     }
 
     public FormFieldBase Build(TModel model, IValidator<TModel> validator, int currentRow)
     {
         var field = CreateFormField(model, validator);
-        field.ApplyConfiguration(formFieldConfiguration);
-        field.ApplyLayoutConfiguration(layoutConfiguration, currentRow);
+        field.ApplyConfiguration(FormFieldConfiguration);
+        field.ApplyLayoutConfiguration(LayoutConfiguration, currentRow);
         return field;
     }
 
     private FormFieldBase CreateFormField(TModel model, IValidator<TModel> validator)
     {
-        var memberInfo = expression.GetMember();
+        var memberInfo = Expression.GetMember();
         var getter = FormFieldAccessorCache.GetCachedGetter<TModel, TProperty>(memberInfo);
         var setter = FormFieldAccessorCache.GetCachedSetter<TModel, TProperty>(memberInfo);
 
         return (this) switch
         {
-            { controlTemplateName: FormFieldNames.CheckBox } => new CheckBoxFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            { controlTemplateName: FormFieldNames.DatePicker } => new DatePickerFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            { controlTemplateName: FormFieldNames.Editor } => new EditorFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            { controlTemplateName: FormFieldNames.Entry } => new EntryFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            { controlTemplateName: FormFieldNames.Slider } => new SliderFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            { controlTemplateName: FormFieldNames.Stepper } => new StepperFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            { controlTemplateName: FormFieldNames.Switch } => new SwitchFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            { controlTemplateName: FormFieldNames.TimePicker } => new TimePickerFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
-            _ => new CustomTemplateFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, controlTemplateName, validator)
+            { FormFieldTemplateName: FormFieldNames.CheckBox } => new CheckBoxFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            { FormFieldTemplateName: FormFieldNames.DatePicker } => new DatePickerFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            { FormFieldTemplateName: FormFieldNames.Editor } => new EditorFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            { FormFieldTemplateName: FormFieldNames.Entry } => new EntryFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            { FormFieldTemplateName: FormFieldNames.Slider } => new SliderFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            { FormFieldTemplateName: FormFieldNames.Stepper } => new StepperFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            { FormFieldTemplateName: FormFieldNames.Switch } => new SwitchFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            { FormFieldTemplateName: FormFieldNames.TimePicker } => new TimePickerFormField<TModel, TProperty>(model, memberInfo.Name, getter, setter, validator),
+            _ => CreateCustomFormField(model, memberInfo.Name, getter, setter, validator)
         };
     }
 
-    public ICheckBoxFormFieldBuilder<TModel> AsCheckBox()
+    protected virtual FormFieldBase CreateCustomFormField(TModel model, string memberName, Func<TModel, TProperty> getter, Action<TModel, TProperty> setter, IValidator<TModel> validator = null)
     {
-        controlTemplateName = FormFieldNames.CheckBox;
-        formFieldConfiguration = new CheckBoxFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
-        return this;
+        throw new ArgumentOutOfRangeException();
     }
 
-    public ICustomTemplateFormFieldBuilder<TModel> AsCustomTemplate(string templateName)
+    public ICheckBoxFormFieldBuilder<TModel> AsCheckBox()
     {
-        controlTemplateName = templateName;
-        formFieldConfiguration = new CustomTemplateFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.CheckBox;
+        FormFieldConfiguration = new CheckBoxFormFieldConfiguration();
+
         return this;
     }
 
     public IDatePickerFormFieldBuilder<TModel> AsDatePicker()
     {
-        controlTemplateName = FormFieldNames.DatePicker;
-        formFieldConfiguration = new DatePickerFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.DatePicker;
+        FormFieldConfiguration = new DatePickerFormFieldConfiguration();
+
         return this;
     }
 
     public IEditorFormFieldBuilder<TModel> AsEditor()
     {
-        controlTemplateName = FormFieldNames.Editor;
-        formFieldConfiguration = new EditorFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.Editor;
+        FormFieldConfiguration = new EditorFormFieldConfiguration();
+
         return this;
     }
 
     public IEntryFormFieldBuilder<TModel> AsEntry()
     {
-        controlTemplateName = FormFieldNames.Entry;
-        formFieldConfiguration = new EntryFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.Entry;
+        FormFieldConfiguration = new EntryFormFieldConfiguration();
+
         return this;
     }
 
     public ISliderFormFieldBuilder<TModel> AsSlider()
     {
-        controlTemplateName = FormFieldNames.Slider;
-        formFieldConfiguration = new SliderFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.Slider;
+        FormFieldConfiguration = new SliderFormFieldConfiguration();
+
         return this;
     }
 
     public IStepperFormFieldBuilder<TModel> AsStepper()
     {
-        controlTemplateName = FormFieldNames.Stepper;
-        formFieldConfiguration = new StepperFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.Stepper;
+        FormFieldConfiguration = new StepperFormFieldConfiguration();
+
         return this;
     }
 
     public ISwitchFormFieldBuilder<TModel> AsSwitch()
     {
-        controlTemplateName = FormFieldNames.Switch;
-        formFieldConfiguration = new SwitchFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.Switch;
+        FormFieldConfiguration = new SwitchFormFieldConfiguration();
+
         return this;
     }
 
     public ITimePickerFormFieldBuilder<TModel> AsTimePicker()
     {
-        controlTemplateName = FormFieldNames.TimePicker;
-        formFieldConfiguration = new TimePickerFormFieldConfiguration();
-        layoutConfiguration = new FormFieldLayoutConfiguration();
-
+        FormFieldTemplateName = FormFieldNames.TimePicker;
+        FormFieldConfiguration = new TimePickerFormFieldConfiguration();
+
         return this;
     }
 
     public ICheckBoxFormFieldBuilder<TModel> WithConfiguration(Action<CheckBoxFormFieldConfiguration> configure)
     {
-        configure?.Invoke((CheckBoxFormFieldConfiguration)formFieldConfiguration);
-        return this;
-    }
-
-    public ICustomTemplateFormFieldBuilder<TModel> WithConfiguration(Action<CustomTemplateFormFieldConfiguration> configure)
-    {
-        configure?.Invoke((CustomTemplateFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((CheckBoxFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public IDatePickerFormFieldBuilder<TModel> WithConfiguration(Action<DatePickerFormFieldConfiguration> configure)
     {
-        configure?.Invoke((DatePickerFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((DatePickerFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public IEditorFormFieldBuilder<TModel> WithConfiguration(Action<EditorFormFieldConfiguration> configure)
     {
-        configure?.Invoke((EditorFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((EditorFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public IEntryFormFieldBuilder<TModel> WithConfiguration(Action<EntryFormFieldConfiguration> configure)
     {
-        configure?.Invoke((EntryFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((EntryFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public ISliderFormFieldBuilder<TModel> WithConfiguration(Action<SliderFormFieldConfiguration> configure)
     {
-        configure?.Invoke((SliderFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((SliderFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public IStepperFormFieldBuilder<TModel> WithConfiguration(Action<StepperFormFieldConfiguration> configure)
     {
-        configure?.Invoke((StepperFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((StepperFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public ISwitchFormFieldBuilder<TModel> WithConfiguration(Action<SwitchFormFieldConfiguration> configure)
     {
-        configure?.Invoke((SwitchFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((SwitchFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public ITimePickerFormFieldBuilder<TModel> WithConfiguration(Action<TimePickerFormFieldConfiguration> configure)
     {
-        configure?.Invoke((TimePickerFormFieldConfiguration)formFieldConfiguration);
+        configure?.Invoke((TimePickerFormFieldConfiguration)FormFieldConfiguration);
         return this;
     }
 
     public ILayoutFieldBuilder WithLayout(Action<FormFieldLayoutConfiguration> configure)
     {
-        configure?.Invoke(layoutConfiguration);
+        configure?.Invoke(LayoutConfiguration);
         return this;
     }
 }

Maui.FluentForms/Builders/IFormFieldBuilder.cs

@@ -7,7 +7,6 @@ namespace Maui.FluentForms.Builders;
 public interface IFormFieldBuilder<TModel>
 {
     ICheckBoxFormFieldBuilder<TModel> AsCheckBox();
-    ICustomTemplateFormFieldBuilder<TModel> AsCustomTemplate(string templateName);
     IDatePickerFormFieldBuilder<TModel> AsDatePicker();
     IEditorFormFieldBuilder<TModel> AsEditor();
     IEntryFormFieldBuilder<TModel> AsEntry();
@@ -28,11 +27,6 @@ public interface ICheckBoxFormFieldBuilder<TModel> : ILayoutFieldBuilder
     ICheckBoxFormFieldBuilder<TModel> WithConfiguration(Action<CheckBoxFormFieldConfiguration> configure);
 }
 
-public interface ICustomTemplateFormFieldBuilder<TModel> : ILayoutFieldBuilder
-{
-    ICustomTemplateFormFieldBuilder<TModel> WithConfiguration(Action<CustomTemplateFormFieldConfiguration> configure);
-}
-
 public interface IDatePickerFormFieldBuilder<TModel> : ILayoutFieldBuilder
 {
     IDatePickerFormFieldBuilder<TModel> WithConfiguration(Action<DatePickerFormFieldConfiguration> configure);

Maui.FluentForms/Extensions/AppHostBuilderExtensions.cs

@@ -2,9 +2,9 @@
 
 public static class AppHostBuilderExtensions
 {
-    public static MauiAppBuilder MapFormFieldContentControl<ContentView>(this MauiAppBuilder builder, string templateName)
+    public static MauiAppBuilder MapFormFieldContentControl<ContentView>(this MauiAppBuilder builder, string formFieldTemplateName)
     {
-        FormFieldDataTemplateSelector.MapFormFieldContentControl<ContentView>(templateName);
+        FormFieldDataTemplateSelector.MapFormFieldContentControl<ContentView>(formFieldTemplateName);
         return builder;
     }
 }

Maui.FluentForms/FormBase.cs

@@ -26,7 +26,14 @@ public IFormFieldBuilder<TModel> FieldFor<TProperty>(Expression<Func<TModel, TPr
     {
         _ = expression ?? throw new ArgumentNullException(nameof(expression));
 
-        var builder = new FormFieldBuilder<TModel, TProperty>(expression);
+        return FieldFor(new FormFieldBuilder<TModel, TProperty>(expression));
+    }
+
+    public TBuilder FieldFor<TBuilder>(TBuilder builder)
+        where TBuilder : IFormFieldBuilder<TModel>
+    {
+        _ = builder ?? throw new ArgumentNullException(nameof(builder));
+
         builders.Add(builder);
         return builder;
     }

Maui.FluentForms/FormFieldDataTemplateSelector.cs

@@ -6,14 +6,14 @@ public class FormFieldDataTemplateSelector : DataTemplateSelector
 {
     private static IDictionary<string, Type> mappings = new Dictionary<string, Type>();
 
-    internal static void MapFormFieldContentControl<ContentView>(string templateName)
+    internal static void MapFormFieldContentControl<ContentView>(string formFieldTemplateName)
     {
-        mappings.Add(templateName, typeof(ContentView));
+        mappings.Add(formFieldTemplateName, typeof(ContentView));
     }
 
     protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
     {
-        var contentControlType = mappings[((FormFieldBase)item).FieldTemplateName];
+        var contentControlType = mappings[((FormFieldBase)item).FormFieldTemplateName];
         return new DataTemplate(contentControlType);
     }
 }

Maui.FluentForms/FormFields/CheckBoxFormField.cs

@@ -1,5 +1,4 @@
-
-using Maui.FluentForms.Configuration;
+using Maui.FluentForms.Configuration;
 using Maui.FluentForms.Validation;
 
 namespace Maui.FluentForms.FormFields;
@@ -11,7 +10,7 @@ public CheckBoxFormField(TModel model, string memberName, Func<TModel, TProperty
     {
     }
 
-    internal override void ApplyConfiguration(IFormFieldConfiguration configuration)
+    public override void ApplyConfiguration(IFormFieldConfiguration configuration)
     {
         // no-op
         return;

Maui.FluentForms/FormFields/DatePickerFormField.cs

@@ -14,7 +14,7 @@ public DatePickerFormField(TModel model, string memberName, Func<TModel, TProper
     {
     }
 
-    internal override void ApplyConfiguration(IFormFieldConfiguration configuration)
+    public override void ApplyConfiguration(IFormFieldConfiguration configuration)
     {
         var typedConfiguration = (DatePickerFormFieldConfiguration)configuration;
 

Maui.FluentForms/FormFields/EditorFormField.cs

@@ -14,7 +14,7 @@ public EditorFormField(TModel model, string memberName, Func<TModel, TProperty>
     {
     }
 
-    internal override void ApplyConfiguration(IFormFieldConfiguration configuration)
+    public override void ApplyConfiguration(IFormFieldConfiguration configuration)
     {
         var typedConfig = (EditorFormFieldConfiguration)configuration;
 

Maui.FluentForms/FormFields/EntryFormField.cs

@@ -21,7 +21,7 @@ public EntryFormField(TModel model, string memberName, Func<TModel, TProperty> g
     {
     }
 
-    internal override void ApplyConfiguration(IFormFieldConfiguration configuration)
+    public override void ApplyConfiguration(IFormFieldConfiguration configuration)
     {
         var typedConfig = (EntryFormFieldConfiguration)configuration;