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[Blazor] Lazy loading - Complete example - Prevent repeated loads #34243

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guardrex merged 3 commits into from
Dec 12, 2024
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[Blazor] Lazy loading - Complete example - Prevent repeated loads #34243

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[Blazor] Lazy loading - Complete example - Prevent repeated loads
hakenr Nov 29, 2024
02254ce
Move flag set line down
guardrex Dec 12, 2024
6d84812
... and the other line!
guardrex Dec 12, 2024
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8 changes: 6 additions & 2 deletions aspnetcore/blazor/webassembly-lazy-load-assemblies.md
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Original file line number Diff line number Diff line change
Expand Up @@ -596,13 +596,15 @@ The assembly is assigned to <xref:Microsoft.AspNetCore.Components.Routing.Router

@code {
private List<Assembly> lazyLoadedAssemblies = new();
private bool grantImaharaRobotControlsAssemblyLoaded;

private async Task OnNavigateAsync(NavigationContext args)
{
try
{
if (args.Path == "robot")
if ((args.Path == "robot") && !grantImaharaRobotControlsAssemblyLoaded)
{
grantImaharaRobotControlsAssemblyLoaded = true;
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@guardrex guardrex Dec 12, 2024

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NIT question on the location of this line ...

Because the component survives an exception on the next two lines, does it make sense to move this line (grantImaharaRobotControlsAssemblyLoaded = true;) to the end after the lazyLoadedAssemblies.AddRange(assemblies); line (i.e., it's only true if we know those two lines executed)?

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@guardrex guardrex Dec 12, 2024

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I'm going to go ahead and move the line down to get this in. I'm about to shoot a bunch of PRs into the live branch.

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@hakenr hakenr Dec 12, 2024

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@guardrex Neither of the two alternatives is perfect. I usually prefer to set the flag before an awaited operation - because with the await there, another navigation might occur while waiting for the assembly to load, leaving the flag still false for the second run.

In this case, since the awaited assembly load won’t cause a critical failure if called repeatedly, I agree that your version is better.

var assemblies = await AssemblyLoader.LoadAssembliesAsync(
new[] { "GrantImaharaRobotControls.{FILE EXTENSION}" });
lazyLoadedAssemblies.AddRange(assemblies);
Expand Down Expand Up @@ -648,13 +650,15 @@ The assembly is assigned to <xref:Microsoft.AspNetCore.Components.Routing.Router

@code {
private List<Assembly> lazyLoadedAssemblies = new List<Assembly>();
private bool grantImaharaRobotControlsAssemblyLoaded;

private async Task OnNavigateAsync(NavigationContext args)
{
try
{
if (args.Path == "robot")
if ((args.Path == "robot") && !grantImaharaRobotControlsAssemblyLoaded)
{
grantImaharaRobotControlsAssemblyLoaded = true;
var assemblies = await AssemblyLoader.LoadAssembliesAsync(
new[] { "GrantImaharaRobotControls.{FILE EXTENSION}" });
lazyLoadedAssemblies.AddRange(assemblies);
Expand Down