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Posted 19 Sep 2020

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Building a Database Application in Blazor - Part 3 - CRUD Edit and View Operations in the UI

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7 Apr 2021MIT6 min read
How to build the CRUD Viewer and Editor Presentation/UI Layer in a Blazor Database Application
This article describes how to build reusable components for Viewing and Editing in the Presentation/UI layer of a Blazor Database Application and how to deploy them in Server and WASM projects.

Introduction

This is the third in a series of articles looking at how to build and structure a Database Application in Blazor.  The articles so far are:

  1. Project Structure and Framework.
  2. Services - Building the CRUD Data Layers.
  3. View Components - CRUD Edit and View Operations in the UI.
  4. UI Components - Building HTML/CSS Controls.
  5. View Components - CRUD List Operations in the UI.

This article looks in detail at building reusable CRUD presentation layer components, specifically Edit and View functionality.   There are significant changes since the first release.

I find it interesting that most programmers try and automate Edit And View forms by building a control builder rather than boilerplating everything else.  Most forms are unique to their record set.   Certain fields can be grouped together and put on the same line.   Text fields change in length depending on how many characters they need.   Building a factory to handle this, plus the added complication of linkages between the control, the dataclass instance and validation, doesn't seem worth it.   The configuration dataset becomes more complicated than the form it's trying to mimic.   For those reasons there's no form builder here, just a set of libary UI component classes to standardise form building.

Sample Project, Code and Links

The repository for the articles has moved to CEC.Database Repository.   You can use it as a template for developing your own applications.   Previous repositories are obselete and will be removed.

There's a SQL script in /SQL in the repository for building the database.   The application can use either a real SQL database or an in-memory SQLite database.

You can see the Server and WASM versions of the project running here on the same site.

Several custom controls are used in the forms.   The detail on these is covered in separate articles:

The Base Forms

All UI components inherit from ComponentBase.   All source files can be viewed on the Github site, and I include references or links to specific code files at appropriate places in the article.   In most places you need to read through the code for detailed commentary on functionality.

RecordFormBase

RecordFormBase is the base abstract class used by the record forms.   It inherits from ComponentBase.   Record forms can be created in several contexts:

  1. As the root component in a RouteView, where the RouteView passes the form the Id via a Parameter.
  2. In a modal dialog within a list or other component.   The ID is passed to the form through a DialogOptions class.  
  3. As an inline editor within another component such as a list, where the component passes the form the Id via a Parameter.

RecordFormBase is designed to detect it's context, specifically the modal dialog context by checking by checking for a cascaded IModalDialog object.   There are two sets of dependancies:

  1. The Id of the record.   This is either passed as a Parameter if the form is hosted in a RouteView or other component, or in a public ModalOptions property of IModalDialog.   Note an Id of -1 means new record while 0 means a default record (0 is the default value for int).
  2. The Exit mechanism.   This is either:
  3. By calling close on Modal if it's in a modal context.
  4. By calling the ExitAction delegate if one if registered.
  5. A default - exit to root.
C#
// Blazor.SPA/Components/Base/RecordFormBase.cs
    public class RecordFormBase<TRecord> : ComponentBase  where TRecord : class, IDbRecord<TRecord>, new()
    {
        [CascadingParameter] public IModalDialog Modal { get; set; }
        [Parameter] public int ID {get; set;}
        [Parameter] public EventCallback ExitAction { get; set; }
        [Inject] protected NavigationManager NavManager { get; set; }
        protected IFactoryControllerService<TRecord> Service { get; set; }
        protected virtual bool IsLoaded => this.Service != null && this.Service.Record != null;
        protected virtual bool HasServices => this.Service != null;
        protected bool _isModal => this.Modal != null;
        protected int _modalId = 0;
        protected int _Id => _modalId != 0 ? _modalId : this.ID;

        protected async override Task OnInitializedAsync()
        {
            await LoadRecordAsync();
            await base.OnInitializedAsync();
        }

        protected virtual async Task LoadRecordAsync()
        {
            this.TryGetModalID();
            await this.Service.GetRecordAsync(this._Id);
        }

        protected virtual bool TryGetModalID()
        {
            if (this._isModal && this.Modal.Options.TryGet<int>("Id", out int value))
            {
                this._modalId = value;
                return true;
            }
            return false;
        }

        protected virtual void Exit()
        {
            if (this._isModal)
                this.Modal.Close(ModalResult.OK());
            else if (ExitAction.HasDelegate)
                ExitAction.InvokeAsync();
            else
                this.NavManager.NavigateTo("/");
        }
    }

EditRecordFormBase

EditRecordFormBase is the base for editor forms.  It inherits from RecordFormBase and implements editing functionality.

It:

  1. Manages the EditContext.
  2. Has a set of Boolean Properties to track state and manage button display/disabled state.
  3. Saves the record.

The Dirty property interfaces with the Modal Dialog to lock it (not allow exit and turn off navigation) when the form is dirty.

C#
// Blazor.SPA/Components/Base/EditRecordFormBase.cs
public abstract class EditRecordFormBase<TRecord> : RecordFormBase<TRecord>, IDisposable where TRecord : class, IDbRecord<TRecord>, new()
{
    /// Edit Context for the Editor - built from the service record
    protected EditContext EditContext { get; set; }

    /// Property tracking the Edit state of the form
    protected bool IsDirty
    {
        get => this._isDirty;
        set
        {
            if (value != this.IsDirty)
            {
                this._isDirty = value;
                if (this._isModal) this.Modal.Lock(value);
            }
        }
    }

    /// model used by the Edit Context
    protected TRecord Model => this.Service?.Record ?? null;

    /// Reference to the form EditContextState control
    protected EditFormState EditFormState { get; set; }

The next set of properties are state properties used in the code and by the razor buttons to control display/disabled state.

C#
protected bool _isNew => this.Service?.IsNewRecord ?? true;
protected bool _isDirty = false;
protected bool _isValid = true;
protected bool _saveDisabled => !this.IsDirty || !this._isValid;
protected bool _deleteDisabled => this._isNew || this._confirmDelete;
protected bool _isLoaded = false;
protected bool _dirtyExit = false;
protected bool _confirmDelete = false;
protected bool _isInlineDirty => (!this._isModal) && this._isDirty;
protected string _saveButtonText => this._isNew ? "Save" : "Update";

LoadRecordAsync calls the base to get the record, creates the EditContext and registers with EditContext.OnFieldChanged.   The other methods handle state change.

C#
protected async override Task OnInitializedAsync()
    => await LoadRecordAsync();

/// Method to load the record
/// calls the base method to load the record and then sets up the EditContext
protected override async Task LoadRecordAsync()
{
    await base.OnInitializedAsync();
    this.EditContext = new EditContext(this.Model);
    _isLoaded = true;
    this.EditContext.OnFieldChanged += FieldChanged;
    if (!this._isNew)
        this.EditContext.Validate();
}

/// Event handler for EditContext OnFieldChanged Event
protected void FieldChanged(object sender, FieldChangedEventArgs e)
{
    this._dirtyExit = false;
    this._confirmDelete = false;
}

/// Method to change edit state
protected void EditStateChanged(bool dirty)
    => this.IsDirty = dirty;


/// Method to change the Validation state
protected void ValidStateChanged(bool valid)
    => this._isValid = valid;

/// IDisposable Interface Implementation
public void Dispose()
    => this.EditContext.OnFieldChanged -= FieldChanged;

Finally the button event handlers to control save and exiting a dirty form.

C#
    /// Method to handle EditForm submission
    protected async void HandleValidSubmit()
    {
        await this.Service.SaveRecordAsync();
        this.EditFormState.UpdateState();
        this._dirtyExit = false;
        await this.InvokeAsync(this.StateHasChanged);
    }

    /// Handler for Delete action
    protected void Delete()
    {
        if (!this._isNew)
            this._confirmDelete = true;
    }

    /// Handler for Delete confirmation
    protected async void ConfirmDelete()
    {
        if (this._confirmDelete)
        {
            await this.Service.DeleteRecordAsync();
            this.IsDirty = false;
            this.DoExit();
        }
    }

    /// Handler for a confirmed exit - i.e.  dirty exit
    protected void ConfirmExit()
    {
        this.IsDirty = false;
        this.DoExit();
    }

    /// Handler to Exit the form, dependant on it context
    protected void DoExit(ModalResult result = null)
    {
        result = result ?? ModalResult.OK();
        if (this._isModal)
            this.Modal.Close(result);
        if (ExitAction.HasDelegate)
            ExitAction.InvokeAsync();
        else
            this.NavManager.NavigateTo("/");
    }
}

Implementing Forms

WeatherForecastViewerForm

The code for the WeatherForecastViewerForm is pretty simple.

  1. Inherit from RecordFormBase and set TRecord as WeatherForecast.
  2. Get the WeatherForecastControllerService and assign it to the base Service property.
C#
public partial class WeatherForecastViewerForm : RecordFormBase<WeatherForecast>
{

    [Inject] private WeatherForecastControllerService ControllerService { get; set; }

    protected async override Task OnInitializedAsync()
    {
        this.Service = this.ControllerService;
        await base.OnInitializedAsync();
    }
}

The majority of the work is in the Razor code.  

  1. There's no Html code, it's all components.   We'll look at UI components in detail on the next article.  
  2. The layout is based on Bootstrap grids.
  3. Column size dictated control size.
  4. UILoader only loads it's content when we have a record to display.
Razor
@namespace Blazor.Database.Components
@inherits RecordFormBase<WeatherForecast>

<UIContainer>
    <UIFormRow>
        <UIColumn>
            <h2>Weather Forecast Viewer</h2>
        </UIColumn>
    </UIFormRow>
</UIContainer>
<UILoader Loaded="this.IsLoaded">
    <UIContainer>
        <UIFormRow>
            <UILabelColumn>
                Date
            </UILabelColumn>
            <UIInputColumn Cols="3">
                <InputReadOnlyText Value="@this.ControllerService.Record.Date.ToShortDateString()"></InputReadOnlyText>
            </UIInputColumn>
            <UIColumn Cols="7"></UIColumn>
        </UIFormRow>
        <UIFormRow>
            <UILabelColumn>
                Temperature °C
            </UILabelColumn>
            <UIInputColumn Cols="2">
                <InputReadOnlyText Value="@this.ControllerService.Record.TemperatureC.ToString()"></InputReadOnlyText>
            </UIInputColumn>
            <UIColumn Cols="8"></UIColumn>
        </UIFormRow>
        <UIFormRow>
            <UILabelColumn>
                Temperature °f
            </UILabelColumn>
            <UIInputColumn Cols="2">
                <InputReadOnlyText Value="@this.ControllerService.Record.TemperatureF.ToString()"></InputReadOnlyText>
            </UIInputColumn>
            <UIColumn Cols="8"></UIColumn>
        </UIFormRow>
        <UIFormRow>
            <UILabelColumn>
                Summary
            </UILabelColumn>
            <UIInputColumn Cols="9">
                <InputReadOnlyText Value="@this.ControllerService.Record.Summary"></InputReadOnlyText>
            </UIInputColumn>
        </UIFormRow>
    </UIContainer>
</UILoader>
<UIContainer>
    <UIFormRow>
        <UIButtonColumn>
            <UIButton AdditionalClasses="btn-secondary" ClickEvent="this.Exit">Exit</UIButton>
        </UIButtonColumn>
    </UIFormRow>
</UIContainer>

WeatherForecastEditorForm

WeatherForecastEditorForm is similar to WeatherForecastViewerForm.

The code is again pretty simple.

  1. Inherit from EditRecordFormBase and set TRecord as WeatherForecast.
  2. Get the WeatherForecastControllerService and assign it to the base Service property.
C#
public partial class WeatherForecastViewerForm : RecordFormBase<WeatherForecast>
{

    [Inject] private WeatherForecastControllerService ControllerService { get; set; }

    protected async override Task OnInitializedAsync()
    {
        this.Service = this.ControllerService;
        await base.OnInitializedAsync();
    }
}

The Razor file is shown below.   It's based on the standard Blazor EditForm with some additional controls.   The same comments made on the Viewer apply here.   In addition:

  1. InlineDialog is a form locking control.   It's enabled by the _isInlineDirty property.   Go to the demo site and edit a record to see it in action.  It's only enabled when the form isn't in a modal context.
  2. EditFormState is a control that tracks the form state, i.e.  the state of the record against the original when the form was loaded.   It links with InlineDialog to control form locking.
  3. ValidationFormState is a custom validation control.
  4. The buttons are tied to the boolean control properties to manage their state.

The custom controls are covered in separate articles referenced in the Links section.   I haven't abstracted this further so you can see a full form in action.   You can move all the Title, Edit Form and button sections into a FormWrapper component.  

Razor
@namespace Blazor.Database.Components
@inherits EditRecordFormBase<WeatherForecast>

<InlineDialog Lock="this._isInlineDirty" Transparent="false">
    <UIContainer>
        <UIFormRow>
            <UIColumn>
                <h2>Weather Forecast Editor</h2>
            </UIColumn>
        </UIFormRow>
    </UIContainer>
    <UILoader Loaded="this._isLoaded">
        <EditForm EditContext="this.EditContext" OnValidSubmit="HandleValidSubmit" class=" px-2 py-3">
            <EditFormState @ref="this.EditFormState"  EditStateChanged="this.EditStateChanged"></EditFormState>
            <ValidationFormState ValidStateChanged="this.ValidStateChanged"></ValidationFormState>
            <UIContainer>
                <UIFormRow>
                    <UILabelColumn>
                        Record ID
                    </UILabelColumn>
                    <UIInputColumn Cols="3">
                        <InputReadOnlyText Value="@this.Model.ID.ToString()" />
                    </UIInputColumn>
                    <UIColumn Cols="3"></UIColumn>
                    <UIValidationColumn>
                        <ValidationMessage For=@(() => this.Model.Date) />
                    </UIValidationColumn>
                </UIFormRow>
                <UIFormRow>
                    <UILabelColumn>
                        Date
                    </UILabelColumn>
                    <UIInputColumn Cols="3">
                        <InputDate class="form-control" @bind-Value="this.Model.Date"></InputDate>
                    </UIInputColumn>
                    <UIColumn Cols="3"></UIColumn>
                    <UIValidationColumn>
                        <ValidationMessage For=@(() => this.Model.Date) />
                    </UIValidationColumn>
                </UIFormRow>
                <UIFormRow>
                    <UILabelColumn>
                        Temperature °C
                    </UILabelColumn>
                    <UIInputColumn Cols="2">
                        <InputNumber class="form-control" @bind-Value="this.Model.TemperatureC"></InputNumber>
                    </UIInputColumn>
                    <UIColumn Cols="4"></UIColumn>
                    <UIValidationColumn>
                        <ValidationMessage For=@(() => this.Model.TemperatureC) />
                    </UIValidationColumn>
                </UIFormRow>
                <UIFormRow>
                    <UILabelColumn>
                        Summary
                    </UILabelColumn>
                    <UIInputColumn>
                        <InputText class="form-control" @bind-Value="this.Model.Summary"></InputText>
                    </UIInputColumn>
                    <UIValidationColumn>
                        <ValidationMessage For=@(() => this.Model.Summary) />
                    </UIValidationColumn>
                </UIFormRow>
            </UIContainer>
            <UIContainer>
                <UIFormRow>
                    <UIButtonColumn>
                        <UIButton Show="true" Disabled="this._deleteDisabled" AdditionalClasses="btn-outline-danger" ClickEvent="() => Delete()">Delete</UIButton>
                        <UIButton Show="this._confirmDelete" AdditionalClasses="btn-danger" ClickEvent="() => this.ConfirmDelete()">Confirm Delete</UIButton>
                        <UIButton Show="true" Disabled="this._saveDisabled" Type="submit" AdditionalClasses="btn-success">@this._saveButtonText</UIButton>
                        <UIButton Show="this._dirtyExit" AdditionalClasses="btn-danger" ClickEvent="() => this.ConfirmExit()">Exit Without Saving</UIButton>
                        <UIButton Show="true" Disabled="this._dirtyExit" AdditionalClasses="btn-dark" ClickEvent="() => this.Exit()">Exit</UIButton>
                    </UIButtonColumn>
                </UIFormRow>
            </UIContainer>
        </EditForm>
    </UILoader>
</InlineDialog>

RouteView Implementations

The RouteView implementation of the viewer is shown below.

  1. Declares the Route with an ID Parameter.
  2. Declares the form WeatherForecastViewerForm.
  3. Passes the ID to the form and attaches a delegate to ExitAction which returns to the fetchdata view.
Razor
// WeatherViewer.razor
@page "/weather/view/{ID:int}"

<WeatherForecastViewerForm ID="this.ID" ExitAction="this.ExitToList"></WeatherForecastViewerForm>

@code {
    [Parameter] public int ID { get; set; }

    [Inject] public NavigationManager NavManager { get; set; }

    private void ExitToList()
        => this.NavManager.NavigateTo("/fetchdata");

}

The editor is exactly the same, but declares the form WeatherForecastEditorForm.

Razor
// WeatherEditor.razor
@page "/weather/edit/{ID:int}"

<WeatherForecastEditorForm ID="this.ID" ExitAction="this.ExitToList"></WeatherForecastEditorForm>

@code {

    [Inject] public NavigationManager NavManager { get; set; }

    [Parameter] public int ID { get; set; }

    private void ExitToList()
        => this.NavManager.NavigateTo("/fetchdata");
}

Wrap Up

That wraps up this article.   We've shown how to build boilerplate code into base forms and how to implement viewer and editor forms.   We'll look in more detail at the list forms and how the viewer and editors are called in a separate article.  

Some key points to note:

  1. The Blazor Server and Blazor WASM code is the same.
  2. Almost all the functionality is implemented in library components.   Most of the application code is Razor markup for the individual record fields.
  3. The Razor files contains controls, not HTML.
  4. Async in used through.

If you're reading this article well into the future, check the readme in the repository for the latest version of the article set.

History

* 19-Sep-2020: Initial version.

* 17-Nov-2020: Major Blazor.CEC library changes.   Change to ViewManager from Router and new Component base implementation.

* 29-Mar-2021: Major updates to Services, project structure and data editing.

License

This article, along with any associated source code and files, is licensed under The MIT License

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About the Author

Shaun C Curtis
Retired Cold Elm
United Kingdom United Kingdom
Ex Geologist, Project Manager, Web Hoster, Business Owner and IT Consultant. Now, a traveller to places less travelled. And part time developer trying to keep up!

If you feel like saying thanks, the next time you see a charity request, DONATE. No matter how small, no matter who, it'll count. If you have a choice in the UK, Barnados.

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