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Value cannot be null (Parameter format)


Product DateInput for Blazor,
DatePicker for Blazor,
DateTimePicker for Blazor,
TimePicker for Blazor,

Grid for Blazor,
ListView for Blazor,
Wizard for Blazor


The Blazor app triggers a null reference exception about a format parameter value. The error may seem to occur on a random basis or consistently, depending on the component configuration.

Error Message

The exception error message can read:

Unhandled exception rendering component: Value cannot be null. (Parameter 'format')


Error: System.ArgumentNullException: Value cannot be null. (Parameter 'format')

Possible Cause

The error is caused by an outdated localization resource file (.resx), which is missing some localization keys.

This exception will occur if the type of TItem is different from the type of the elements in the args.Data collection.


There are two places to get Telerik Blazor localization files:

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