|
| 1 | +--- |
| 2 | +title: InitMediaQueryWidget Throws JsonException |
| 3 | +description: Learn how to troubleshoot and find the cause for a JsonException that may be thrown by the Telerik InitMediaQueryWidget method. |
| 4 | +type: troubleshooting |
| 5 | +page_title: InitMediaQueryWidget Throws JsonException Due to Invalid Cast |
| 6 | +slug: mediaquery-kb-initmediaquery-jsonexception |
| 7 | +tags: blazor, mediaquery, serialization |
| 8 | +ticketid: 1676092, 1680874 |
| 9 | +res_type: kb |
| 10 | +--- |
| 11 | + |
| 12 | +## Environment |
| 13 | + |
| 14 | +<table> |
| 15 | + <tbody> |
| 16 | + <tr> |
| 17 | + <td>Product</td> |
| 18 | + <td> |
| 19 | + MediaQuery for Blazor |
| 20 | + </td> |
| 21 | + </tr> |
| 22 | + </tbody> |
| 23 | +</table> |
| 24 | + |
| 25 | +## Description |
| 26 | + |
| 27 | +A Blazor app may throw a runtime JSON serialization exception on startup that is similar to: |
| 28 | + |
| 29 | +```C#.skip-repl |
| 30 | +Microsoft.JSInterop.JSException: An exception occurred executing JS interop: DeserializeUnableToConvertValue, System.Boolean Path: $ | LineNumber: 0 | BytePositionInLine: 4.. See InnerException for more details. |
| 31 | +
|
| 32 | + ---> System.Text.Json.JsonException: DeserializeUnableToConvertValue, System.Boolean Path: $ | LineNumber: 0 | BytePositionInLine: 4. |
| 33 | + ---> System.InvalidOperationException: InvalidCast, Null, boolean |
| 34 | + at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_ExpectedBoolean(JsonTokenType ) |
| 35 | + at System.Text.Json.Utf8JsonReader.GetBoolean() |
| 36 | +
|
| 37 | + ... |
| 38 | +
|
| 39 | + at Microsoft.JSInterop.JSRuntime.<InvokeAsync>.MoveNext() |
| 40 | + at Telerik.Blazor.Components.TelerikMediaQuery.InitMediaQueryWidget() |
| 41 | + at Telerik.Blazor.Components.TelerikMediaQuery.OnAfterRenderAsync(Boolean firstRender) |
| 42 | +``` |
| 43 | + |
| 44 | +or |
| 45 | + |
| 46 | +```C#.skip-repl |
| 47 | +Microsoft.JSInterop.JSException: An exception occurred executing JS interop: The JSON value could not be converted to System.Boolean. Path: $ | LineNumber: 0 | BytePositionInLine: 4.. See InnerException for more details. |
| 48 | +
|
| 49 | + ---> System.Text.Json.JsonException: The JSON value could not be converted to System.Boolean. Path: $ | LineNumber: 0 | BytePositionInLine: 4. |
| 50 | + ---> System.InvalidOperationException: Cannot get the value of a token type 'Null' as a boolean. |
| 51 | + at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_ExpectedBoolean(JsonTokenType tokenType) |
| 52 | + at System.Text.Json.Utf8JsonReader.GetBoolean() |
| 53 | + ... |
| 54 | +
|
| 55 | + at Microsoft.JSInterop.JSRuntime.<InvokeAsync>.MoveNext() |
| 56 | + at Telerik.Blazor.Components.TelerikMediaQuery.InitMediaQueryWidget() |
| 57 | + at Telerik.Blazor.Components.TelerikMediaQuery.OnAfterRenderAsync(Boolean firstRender) |
| 58 | +``` |
| 59 | + |
| 60 | +## Cause |
| 61 | + |
| 62 | +The [`TelerikRootComponent`](slug:rootcomponent-overview) creates a few [MediaQuery](slug:mediaquery-overview) components. These MediaQuery instances are responsible for the [adaptive behavior of all Telerik dropdowns and popups](slug:adaptive-rendering). During initialization, each Telerik MediaQuery component performs a JSInterop call in `OnAfterRenderAsync` that returns a boolean value back to the .NET runtime. This bool value shows whether the current browser viewport size matches the MediaQuery `Media` parameter value. |
| 63 | + |
| 64 | +An JSON exception in the above algorithm indicates that the received value cannot be converted to boolean type. This can happen if the application is using a third-party package or middleware (for example, Serilog) that overrides the .NET serialization mechanism. As a result, the .NET runtime may receive `null` instead of `true` or `false`. |
| 65 | + |
| 66 | +## Solution |
| 67 | + |
| 68 | +The recommended approach is to modify the app configuration or third-party tooling, so that the .NET serialization works by default. |
| 69 | + |
| 70 | +## Suggested Workaround |
| 71 | + |
| 72 | +In some cases, it may be possible to avoid the JSON error by rendering all Razor components in the app with a delay in `OnAfterRenderAsync`: |
| 73 | + |
| 74 | +>caption MainLayout.razor |
| 75 | +
|
| 76 | +````RAZOR.skip-repl |
| 77 | +@inherits LayoutComponentBase |
| 78 | +
|
| 79 | +@if (ShouldRenderApp) |
| 80 | +{ |
| 81 | + <TelerikRootComponent> |
| 82 | + @Body |
| 83 | + </TelerikRootComponent> |
| 84 | +} |
| 85 | +
|
| 86 | +@code { |
| 87 | + private bool ShouldRenderApp { get; set; } |
| 88 | +
|
| 89 | + protected override async Task OnAfterRenderAsync(bool firstRender) |
| 90 | + { |
| 91 | + if (firstRender) |
| 92 | + { |
| 93 | + await Task.Delay(1); |
| 94 | +
|
| 95 | + ShouldRenderApp = true; |
| 96 | + StateHasChanged(); |
| 97 | + } |
| 98 | +
|
| 99 | + await base.OnAfterRenderAsync(firstRender); |
| 100 | + } |
| 101 | +} |
| 102 | +```` |
| 103 | + |
| 104 | +## See Also |
| 105 | + |
| 106 | +* [DataSourceRequest Filters not Working When You Add Reporting or Newtonsoft.Json](slug:common-kb-newtonsoft-breaks-datasourcerequest-serialization) |
| 107 | +* [Chart not Working with Newtonsoft.Json Properties](slug:chart-kb-newtonsoft-seialization-settings) |
| 108 | +* [Troubleshooting JavaScript Errors](slug:troubleshooting-js-errors) |
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