static LambdaExpression GetExpansion(MemberInfo mi)
{
ExpressionFieldAttribute efa = mi.GetCustomAttribute<ExpressionFieldAttribute>();
if (efa == null)
return null;
if (efa.Name == "auto")
throw new InvalidOperationException($"The {nameof(ExpressionFieldAttribute)} for {mi.DeclaringType.TypeName()}.{mi.MemberName()} has the default value 'auto'.\r\nMaybe Signum.MSBuildTask is not running in assemby {mi.DeclaringType.Assembly.GetName().Name}?");
Type type = mi.DeclaringType;
FieldInfo fi = type.GetField(efa.Name, BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);
if (fi == null)
throw new InvalidOperationException("Expression field '{0}' not found on '{1}'".FormatWith(efa.Name, type.TypeName()));
var obj = fi.GetValue(null);
if (obj == null)
throw new InvalidOperationException("Expression field '{0}' is null".FormatWith(efa.Name));
var result = obj as LambdaExpression;
if (result == null)
throw new InvalidOperationException("Expression field '{0}' does not contain a lambda expression".FormatWith(efa.Name, type.TypeName()));
return result;
}