System.ArgumentNullException: 'X' requires a value for the 'Expression' property

This is a common Blazor exception that occurs if an EditForm’s editor does not use two-way binding.

DevExpress.Blazor.DxComboBox requires a value for the ‘ValueExpression’ property. It is specified automatically when you use two-way binding (‘bind-Value’).

To fix the issue, do one of the following:

  • Specify the Expression property for the properties you use. For example, if you use the Value property and the ValueChanged event separately, also specify the ValueExpression property.
    <DxComboBox Data="@Strings"
        Value="@Value" 
        ValueChanged="@ValueChanged"
        ValueExpression="@(() => Value )">
    </DxComboBox>
    
  • Implement the two-way binding in the EditForm.