/// <summary>
/// Throws an exception when the field in question is null.
/// </summary>
/// <typeparam name="T">The runtime type of the field.</typeparam>
/// <param name="predicate">An expression of type <see cref="Func{T}"/> which returns a field.</param>
/// <exception cref="ArgumentNullException">Thrown when the field is null.</exception>
public static void IfNull <T>(Expression <Func <T> > predicate)
{
FieldInfo fieldInfo = FieldExpressions.GetField(predicate);
object value = fieldInfo
.GetValue(((ConstantExpression)((MemberExpression)predicate.Body).Expression).Value);
if (value == null)
{
throw new ArgumentNullException(fieldInfo.Name);
}
}
/// <summary>
/// Throws an exception when the collection based field in question is null or empty.
/// </summary>
/// <typeparam name="T">The runtime type of the field.</typeparam>
/// <param name="predicate">An expression of type <see cref="Func{T}" /> which returns a field./></param>
// TODO: document the exceptions thrown
public static void IfNullOrEmpty <T>(Expression <Func <T> > predicate)
{
FieldInfo fieldInfo = FieldExpressions.GetField(predicate);
Do.If(!typeof(IEnumerable).IsAssignableFrom(fieldInfo.FieldType), () => {
throw new InvalidOperationException(string.Format("Field {0} is not an IEnumerable.",
fieldInfo.Name));
});
object value = fieldInfo
.GetValue(((ConstantExpression)((MemberExpression)predicate.Body).Expression).Value);
if (value == null)
{
throw new ArgumentNullException(fieldInfo.Name);
}
IEnumerable enumerable = (IEnumerable)value;
IEnumerator enumerator = enumerable.GetEnumerator();
enumerator.Reset();
int i = 0;
while (enumerator.MoveNext() && i == 0)
{
i++;
}
if (i == 0)
{
throw new InvalidOperationException(string.Format("Field {0} should not be empty.", fieldInfo.Name));
}
}