SelfBuildingRazorForm.cshtml

@model EntityBase
@using System.ComponentModel
@using System.ComponentModel.DataAnnotations
@using System.Reflection
@using Microsoft.AspNetCore.Mvc.Localization
@using Microsoft.Extensions.Localization

@inject IHtmlLocalizer<DataAnnotationResources> DataAnnotationLocalizer
@inject IStringLocalizer<SharedResources> SharedLocalizer

@{
    bool IsReadOnly(CustomAttributeData a) => a.AttributeType == typeof(ReadOnlyAttribute) && (bool)a.ConstructorArguments[0].Value;
    bool IsHidden(CustomAttributeData a) => a.AttributeType == typeof(KeyAttribute) || a.AttributeType == typeof(HiddenInputAttribute);
    
    // Virtual Properties are relationship proxies.
    var nonVirtualProps = Model.GetType().GetProperties().Where(p => !p.GetGetMethod().IsVirtual).ToArray();
    
    // Sort the fields into buckets.
    var regularInputProperties = nonVirtualProps.Where(p =>
            p.SetMethod != null
            && !p.CustomAttributes.Any(IsHidden)
            && !p.CustomAttributes.Any(IsReadOnly)
        ).OrderBy(p => p.CustomAttributes.FirstOrDefault(a =>
            a.AttributeType == typeof(DisplayAttribute))?.NamedArguments.FirstOrDefault(arg =>
                arg.MemberName == "Order").TypedValue.Value).ToArray();

    var hiddenInputProperties = nonVirtualProps.Where(p => p.CustomAttributes.Any(IsHidden))
        .OrderBy(p =>
            p.CustomAttributes.FirstOrDefault(a =>
                a.AttributeType == typeof(DisplayAttribute))?.NamedArguments.FirstOrDefault(arg =>
                    arg.MemberName == "Order").TypedValue.Value).ToArray();

    var readOnlyProperties = nonVirtualProps.Where(p => p.CustomAttributes.Any(IsReadOnly))
        .OrderBy(p =>
            p.CustomAttributes.FirstOrDefault(a =>
                a.AttributeType == typeof(DisplayAttribute))?.NamedArguments.FirstOrDefault(arg =>
                    arg.MemberName == "Order").TypedValue.Value).ToArray();


    // Used in row building below.
    var rowFlag = false;
    const string colCap = @"
</div>
<div class=""col-md-6 col-12"">";
    const string rowCap = @"
</div>
</div>
<div class=""form-row"">
<div class=""col-md-6 col-12"">";
}

<form method="post">
    <div class="form-row">
        <div class="col-12">
            <div asp-validation-summary="All" class="text-danger"></div>
            @foreach (var prop in hiddenInputProperties)
            {
                <input type="hidden" id="@prop.Name" name="@prop.Name" value="@prop.GetValue(Model)">
            }
            @if (Model.GetId() != Guid.Empty)
            {
                <input type="hidden" id="RecordId" name="RecordId" value="@Model.GetId()">
            }
            <input type="hidden" id="CreatedBy" name="CreatedBy" value="@Model.CreatedBy">
            <input type="hidden" id="CreatedDate" name="CreatedDate" value="@Model.CreatedDate">
            <input type="hidden" id="ModifiedBy" name="ModifiedBy" value="@Model.ModifiedBy">
            <input type="hidden" id="ModifiedDate" name="ModifiedDate" value="@Model.ModifiedDate">
            <input type="hidden" id="IsActive" name="IsActive" value="@(Model.IsActive ? "true" : "false")">
        </div>
    </div>
    <div class="form-row">
        <div class="col-md-6 col-12">
            @foreach (var prop in regularInputProperties)
            {
                //AttributeCollection attributes = TypeDescriptor.GetProperties(Model)[prop.Name].Attributes;
                //var isReadOnly = attributes[typeof(ReadOnlyAttribute)].Equals(ReadOnlyAttribute.Yes);

                var uiHintAttribute = prop.CustomAttributes
                    .FirstOrDefault(a =>a.AttributeType == typeof(UIHintAttribute));

                var displayName = (string)prop.CustomAttributes
                    .FirstOrDefault(a => a.AttributeType == typeof(DisplayNameAttribute))?.ConstructorArguments[0].Value
                                  ?? (string)prop.CustomAttributes
                                      .FirstOrDefault(a => a.AttributeType == typeof(DisplayAttribute))?.NamedArguments
                                      .FirstOrDefault(arg => arg.MemberName == "Name").TypedValue.Value;

                if (string.IsNullOrEmpty(displayName))
                {
                    continue;
                }
                var displayFormatString = (string)prop.CustomAttributes.FirstOrDefault(a =>
                    a.AttributeType == typeof(DisplayFormatAttribute))?.NamedArguments.FirstOrDefault(arg =>
                        arg.MemberName == "DataFormatString").TypedValue.Value;

                var localizedDisplayName = DataAnnotationLocalizer[displayName];

                var propType = prop.PropertyType;
                if (propType.IsGenericType && propType.GetGenericTypeDefinition() == typeof(Nullable<>))
                {
                    // Get the real type of this nullable property.
                    propType = propType.GetGenericArguments().Single();
                }
                var inputType = "";
                if (propType == typeof(Guid))
                {
                    <div class="form-group">
                        <label for="@prop.Name">
                            @localizedDisplayName
                        </label>
                        <select class="form-control" name="@prop.Name" id="@prop.Name">
                            <option value="">@SharedLocalizer["SelectDefaultItem"]</option>
                            @{
                                var options = (IEnumerable<SelectListItem>)ViewData[$"{prop.Name}Options"];
                                if (options != null && options.Any())
                                {
                                    foreach (var option in options)
                                    {
                                        if (prop.GetValue(Model)?.ToString().Equals(option.Value, StringComparison.InvariantCultureIgnoreCase) ?? false)
                                        {
                                            <option value="@option.Value" selected="selected">@option.Text</option>
                                        }
                                        else
                                        {
                                            <option value="@option.Value">@option.Text</option>
                                        }
                                    }
                                }
                            }
                        </select>
                    </div>
                }
                else if (uiHintAttribute != null && string.Equals(uiHintAttribute.ConstructorArguments[0].Value.ToString(), "DropDownList", StringComparison.InvariantCultureIgnoreCase))
                {
                    <div class="form-group">
                        <label for="@prop.Name">
                            @localizedDisplayName
                        </label>
                        <select class="form-control" name="@prop.Name" id="@prop.Name">
                            <option value="">@SharedLocalizer["SelectDefaultItem"]</option>
                            @{
                                var options = (IEnumerable<SelectListItem>)ViewData[$"{prop.Name}Options"];
                                if (options != null && options.Any())
                                {
                                    foreach (var option in options)
                                    {
                                        if (prop.GetValue(Model)?.ToString().Equals(option.Value, StringComparison.InvariantCultureIgnoreCase) ?? false)
                                        {
                                            <option value="@option.Value" selected="selected">@option.Text</option>
                                        }
                                        else
                                        {
                                            <option value="@option.Value">@option.Text</option>
                                        }
                                    }
                                }
                            }
                        </select>
                    </div>
                }
                else if (propType == typeof(string))
                {
                    inputType = "text";
                }
                else if (propType == typeof(int) || propType == typeof(decimal))
                {
                    inputType = "number";
                }
                else if (propType == typeof(DateTimeOffset))
                {
                    inputType = "datetime";
                }
                else if (propType == typeof(bool))
                {
                    inputType = "checkbox";
                }
                else
                {
                    throw new NotImplementedException($"The Editor Template lacks a display definition for type {propType}.");
                }

                if (inputType == "checkbox")
                {
                    <div class="btn-group-toggle" data-toggle="buttons">
                        <label class="btn btn-secondary">
                            @Html.CheckBox(prop.Name, (bool)prop.GetValue(Model)) @localizedDisplayName
                        </label>
                    </div>
                }
                else
                {
                    <div class="form-group">
                        <label for="@prop.Name">
                            @localizedDisplayName
                        </label>
                        <input class="form-control" type="@inputType" id="@prop.Name" name="@prop.Name" 
                               value="@(string.IsNullOrEmpty(displayFormatString) 
                                            ? prop.GetValue(Model) 
                                            : string.Format(displayFormatString, prop.GetValue(Model)))">
                    </div>
                }
                if (!rowFlag)
                {
                    @Html.Raw(colCap)
                    rowFlag = true;
                }
                else
                {
                    @Html.Raw(rowCap)
                    rowFlag = false;
                }
            }

        </div>
    </div>
    <div class="form-row">
        <div class="col-12">
            <div class="form-group">
                <input type="submit" value="Save" class="btn btn-primary" />
            </div>
        </div>
    </div>
</form>