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Content Render Modes in Blazor Tabs component

In Blazor Tabs, you can render the content of the Tabs based on the scenario. The content rendering of tabs can be done by the following three different ways.

Dynamic rendering

This mode is the default one in which the content of the selected tab alone will be loaded and available in DOM initially and it will be replaced with corresponding content if you select the tab dynamically. Since in this mode, the browser maintains the DOM with current active tab content alone, page loading performance is increased with rendering DOM. But the Tabs doesn’t maintain its current state since every time tab loaded with fresh content.

In the following code example, there are two tabs. The first tab have a login page and second tab have Grid component. The second tab Grid component will be rendered in the DOM only when login is completed. The second tab will be replaced the first tab in the DOM.

@using Syncfusion.Blazor.Buttons
@using Syncfusion.Blazor.Navigations
@using Syncfusion.Blazor.Grids

<SfTab LoadOn="ContentLoad.Dynamic" @bind-SelectedItem="@SelectedTab">
    <TabItems>
        <TabItem Disabled="@Disabled">
            <HeaderTemplate>Login</HeaderTemplate>
            <ContentTemplate>
                <div class="login-form">
                    <div class='wrap'>
                        <div id="heading">Sign in to view the Grid</div>
                        <div id="input-container">
                            <div class="e-float-input e-input-group">
                                <input type="text" @bind-value="@UserName" required />
                                <span class="e-float-line"></span>
                                <label class="e-float-text">Username</label>
                            </div>
                            <div class="e-float-input e-input-group">
                                <input type="password" @bind-value="@Password" required />
                                <span class="e-float-line"></span>
                                <label class="e-float-text">Password</label>
                            </div>
                        </div>
                        <div class="button-contain">
                            <SfButton @onclick="@OnClicked">Log in</SfButton>
                        </div>
                    </div>
                </div>
            </ContentTemplate>
        </TabItem>
        <TabItem Disabled="@DisableTab">
            <HeaderTemplate>Grid</HeaderTemplate>
            <ContentTemplate>
                <SfGrid DataSource="@Orders">
                    <GridPageSettings></GridPageSettings>
                    <GridColumns>
                        <GridColumn Field=@nameof(Order.OrderID) HeaderText="Order ID" TextAlign="TextAlign.Right" Width="120"></GridColumn>
                        <GridColumn Field=@nameof(Order.CustomerID) HeaderText="Customer Name" Width="130"></GridColumn>
                        <GridColumn Field=@nameof(Order.OrderDate) HeaderText=" Order Date" Format="yMd" Type="ColumnType.Date" TextAlign="TextAlign.Right" Width="150"></GridColumn>
                        <GridColumn Field=@nameof(Order.Freight) HeaderText="Freight" Format="C2" TextAlign="TextAlign.Right" Width="120"></GridColumn>
                    </GridColumns>
                </SfGrid>
            </ContentTemplate>
        </TabItem>
    </TabItems>
</SfTab>

@code {
    private string UserName { get; set; } = "";
    private string Password { get; set; } = "";
    private Boolean DisableTab { get; set; } = true;
    private Boolean Disabled { get; set; } = false;
    private int SelectedTab { get; set; } = 0;
    public List<Order> Orders { get; set; }

    protected override void OnInitialized()
    {
        Orders = Enumerable.Range(1, 6).Select(x => new Order()
        {
            OrderID = 1000 + x,
            CustomerID = (new string[] { "ALFKI", "ANANTR", "ANTON", "BLONP", "BOLID" })[new Random().Next(5)],
            Freight = 2.1 * x,
            OrderDate = DateTime.Now.AddDays(-x),
        }).ToList();
    }

    private void OnClicked()
    {
        if (this.UserName == "" && this.Password == "")
        {
            Console.WriteLine("clicked");
        }
        else if (this.UserName == "")
        {
            Console.WriteLine("Enter the username");
        }
        else if (this.Password == "")
        {
            Console.WriteLine("Enter the password");
        }
        else if (this.UserName.Length < 4)
        {
            Console.WriteLine("Username must be minimum 4 characters");
        }
        else
        {
            this.UserName = "";
            this.Password = "";
            this.DisableTab = false;
            this.Disabled = true;
            this.SelectedTab = 1;
        }
    }

    public class Order
    {
        public int? OrderID { get; set; }
        public string CustomerID { get; set; }
        public DateTime? OrderDate { get; set; }
        public double? Freight { get; set; }
    }
}

In this mode, if you want to maintain the state, you have to handle it in application end.

On Demand rendering or lazy loading

You can set this mode to our Tabs by setting ContentLoad.Demand to the property LoadOn. In this mode, the content of the selected tab alone will be loaded initially. The content of the selected tab will be rendered on selection. The content of the tabs which were loaded once will be maintained in the DOM. In this mode, since the selected tab content alone rendered on initial load and maintained the other tabs on selection in the DOM, state of the tabs like scroller position, form values etc.., will be maintained. The OnInitialized life cycle method will trigger whenever the tab is switched.

In the following code example, Calendar and Scheduler have been rendered in first and second tab respectively. Initially, Scheduler is not available once the second tab is selected, scheduler will be rendered. Both calendar and scheduler will be maintained in DOM, changing the date either in calendar or scheduler will change the date in other.

@using Syncfusion.Blazor.Calendars
@using Syncfusion.Blazor.Navigations
@using Syncfusion.Blazor.Schedule

<SfTab LoadOn="ContentLoad.Demand">
    <TabItems>
        <TabItem>
            <HeaderTemplate>Calendar</HeaderTemplate>
            <ContentTemplate>
                <SfCalendar TValue="DateTime" @bind-Value="@SelectedDate"></SfCalendar>
            </ContentTemplate>
        </TabItem>
        <TabItem>
            <HeaderTemplate>Scheduler</HeaderTemplate>
            <ContentTemplate>
                <SfSchedule TValue="AppointmentData" Height="450px" @bind-SelectedDate="@SelectedDate">
                    <ScheduleViews>
                        <ScheduleView Option="View.Day"></ScheduleView>
                    </ScheduleViews>
                </SfSchedule>
            </ContentTemplate>
        </TabItem>
    </TabItems>
</SfTab>

@code {
    private DateTime SelectedDate { get; set; } = new DateTime(2020, 1, 10);
    public class AppointmentData
    {
        public int Id { get; set; }
        public string Subject { get; set; }
        public DateTime StartTime { get; set; }
        public DateTime EndTime { get; set; }
    }
}

On initial rendering

You can set this mode to our Tabs by setting ContentLoad.OnInit to the property LoadOn. In this mode, the content of all the tabs will be rendered on initial load and maintained in the DOM. You can use this mode, when you have less number of tabs and you need to maintain the state of tabs. In this mode, you can access the reference of components rendered in other tabs.

In the following example, all the three tabs are rendered in initial load itself and the data entered in the first tab will be maintained even when second or third tab is in active state.

@using Syncfusion.Blazor.Navigations
@using Syncfusion.Blazor.Inputs
@using Syncfusion.Blazor.Buttons

<SfTab LoadOn="ContentLoad.Init" @bind-SelectedItem="@SelectedTab">
   <TabItems>
       <TabItem>
           <HeaderTemplate>Sign in</HeaderTemplate>
           <ContentTemplate>
               <div id="User details" style="padding:10px">
                   <form id="formId">
                       <div class="form-group">
                           <div class="e-float-input">
                               <SfTextBox Placeholder="Enetr name" @bind-Value="UserName"></SfTextBox>
                           </div>
                           <div class="e-float-input">
                               <SfTextBox Placeholder="Email" @bind-Value="MailAddress" Type="InputType.Email"></SfTextBox>
                           </div>
                       </div>
                   </form>
                   <div style="text-align: center">
                       <SfButton @onclick="@OnSignin">Sign in</SfButton>
                       <SfButton @onclick="@OnSkip">Skip</SfButton>
                       @if (EmptyField)
                       {
                           <div class="Error">* Please fill all fields</div>
                       }
                   </div>
               </div>
           </ContentTemplate>
       </TabItem>
       <TabItem>
           <HeaderTemplate>Syncfusion Blazor</HeaderTemplate>
           <ContentTemplate>
               <p>You can check out our Syncfusion Blazor demo here - https://blazor.syncfusion.com/demos/ </p>
               <br />
               <p>Also user guide will be avail here - https://blazor.syncfusion.com/documentation/introduction/</p>
           </ContentTemplate>
       </TabItem>
       <TabItem>
           <HeaderTemplate>Feedback</HeaderTemplate>
           <ContentTemplate>
               <div id="Feedback_Form" style="padding:10px">
                   <form id="formId">
                       <div class="form-group">
                           <div class="e-float-input">
                               <SfTextBox Placeholder="Enetr name" @bind-Value="UserName"></SfTextBox>
                           </div>
                           <div class="e-float-input">
                               <SfTextBox @bind-Value="MailAddress" Placeholder="Email" Type="InputType.Email"></SfTextBox>
                           </div>
                           <div class="e-float-input">
                               <SfTextBox @bind-Value="Comments" Placeholder="Share your comments"></SfTextBox>
                           </div>
                       </div>
                   </form>
                   <div style="text-align: center">
                       <SfButton @onclick="@OnSubmit">Submit</SfButton>
                       @if (EmptyField)
                       {
                           <div class="Error">* Please fill all fields</div>
                       }
                   </div>
               </div>
           </ContentTemplate>
       </TabItem>
   </TabItems>
</SfTab>

@code {
   private string UserName;
   private string MailAddress;
   private string Comments;
   private int SelectedTab = 0;
   public Boolean EmptyField { get; set; } = false;
   private void OnSignin()
   {
       if (this.UserName == null || this.MailAddress == null)
       {
           EmptyField = true;
       }
       else
       {
           EmptyField = false;
           this.SelectedTab = 1;
       }
   }
   private void OnSkip()
   {
       this.SelectedTab = 1;
   }
   public void OnSubmit()
   {
       if (this.UserName == null || this.MailAddress == null || this.Comments == null)
       {
           EmptyField = true;
       }
       else
       {
           EmptyField = false;
           this.UserName = null;
           this.MailAddress = null;
           this.Comments = null;
       }
   }
}