System.ArgumentNullException: 'Value cannot be null. Arg_ParamName_Name'

    public enum TestEnum : int
    {
        None = 0,
        Type1 = 1
    }
    public class TestTable
    {
        public long ID { get; set; }
        public TestEnum TestType { get; set; }
    }

new TestTable() 
{
    ID = reader.GetInt64(0),
    TestEnum = Convert(Parse(TestEnum, GetName(TestEnum, Convert(reader.GetInt32(1), Object)), True), TestEnum)
}

Assume reader.GetInt32(1) returns "4". But "4" doesn't exist in TestEnum. Then GetName returns "null". Parse throws the error...

long dbValue = 4; //note, in this case the db-type differs from the corresponding enum-type int
var baseType = typeof(TestEnum).GetEnumUnderlyingType();

object convertedDbValue = dbValue;
if (baseType != dbValue.GetType()) //if dbValue-Type differs from underlying enum-type
	convertedDbValue = Convert.ChangeType(dbValue, baseType); //ex. long to int

object result;
if (Enum.IsDefined(typeof(TestEnum), convertedDbValue))
	result = Enum.ToObject(typeof(TestEnum), dbValue);
else
	result = default(TestEnum);
return result;

internal static Expression ConvertExpressionToEnumExpressionForNonString(Expression expression, Type toEnumType)
{
	Type baseType = toEnumType.GetEnumUnderlyingType();
	if (baseType != expression.Type)
	{
		var convertMethod = StaticType.Convert.GetMethod("ChangeType", new[] { StaticType.Object, StaticType.Type });
		var convertParameters = new Expression[]
		{
			Expression.Convert(expression, StaticType.Object),
			Expression.Constant(baseType)
		};
		expression = Expression.Call(convertMethod, convertParameters);
	}
	else
		expression = Expression.Convert(expression, StaticType.Object);

	var isDefinedMethod = StaticType.Enum.GetMethod("IsDefined", new[] { StaticType.Type, StaticType.Object });
	var isDefinedParameters = new Expression[]
	{
			Expression.Constant(toEnumType),
			expression
	};            
	var isDefinedExpression = Expression.Call(isDefinedMethod, isDefinedParameters);

	var toObjectMethod = StaticType.Enum.GetMethod("ToObject", new[] { StaticType.Type, StaticType.Object });
	var toObjectParameters = new Expression[]
	{
			Expression.Constant(toEnumType),
			expression
	};
	var toObjectExpression = Expression.Call(toObjectMethod, toObjectParameters);

	var defaultExpression = Expression.Convert(Expression.Default(toEnumType), StaticType.Object);

	return Expression.Condition(isDefinedExpression, toObjectExpression, defaultExpression);
}