How do I pass values from one page to another in Blazor WebAssembly?

By using Blazor route parameters, you can pass values from one page to another page. Use NavigationManager to pass a value and route the parameter to another page.

Follow this example to achieve passing values from one page to another.
[Page1.razor]

@page "/page1"
@inject NavigationManager UriHelper

<h3>Click button to pass the value to other page.</h3>
<button class="btn btn-primary" @onclick="OnClick">Pass Value</button>

@code {

    private string parameter = "ParameterValue";
    private void OnClick()
    {
        UriHelper.NavigateTo($"counter/{parameter}");
    }
}

Get the passed Page1 parameter value in Page2.
[Page2.razor]

@page "/page2/{Value}"

<p>@Value</p>

@code {
    [Parameter]
    public string Value { get; set; }

}

Refer to this link for more details.