Code Inspection: Possible 'System.InvalidOperationException'

Before you cast a variable of a nullable type to its underlying type, you should make sure that the value is not null. In the example below, we have a nullable double x, and the expression (double)x will throw an exception if x is null.

ReSharper suggests checking for null:

            
public void Method(double? x)
{
    var y = (double)x;
    Console.WriteLine(y);
}

        

            
public void Method(double? x)
{
    if (x != null)
    {
        var y = (double)x;
        Console.WriteLine(y);
    }
}

        

Alternatively, ReSharper can add the assertion that the expression is not null:

            
public void Method(double? x)
{
    var y = (double)x;
    Console.WriteLine(x);
}

        

            
public void Method(double? x)
{
    Debug.Assert(x != null, "x != null");
    var y = (double)x;
    Console.WriteLine(x);
}

        

Last modified: 21 July 2022