Pass an Enum as parameter in DynamicExpression

Question

I am using ParseLambda from System.Linq.DynamicExpression namespace. More info can be found on ScottGu's blog.

The following code throws Unknown identifier 'TeamType' exception

public bool CheckCondition()
{
    try
    {
        var condition = "CurrentUser.CurrentTeamType == TeamType.Admin";
        var currentUserParameter = Expression.Parameter(typeof(UserInfo), "CurrentUser");
        var dynamicExpression = System.Linq.Dynamic.DynamicExpression.ParseLambda(new[] { currentUserParameter}, null, condition);
        var result = dynamicExpression.Compile().DynamicInvoke(CurrentUserInfo);
        return Convert.ToBoolean(result);
    }
    catch(Exception ex)
    {
      // do some stuff then throw it again
      throw ex;
    }
}

public enum TeamType
{
    Admin = 1,
    AnotherType = 2
}

public class UserInfo
{
    public short UserId { get; set; }
    public string UserName { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
    public TeamType CurrentTeamType { get; set; }
}

CurrentUserInfo is just an instance of UserInfo;

My question is what can I do so TeamType will be recognized, or how can I pass the enum as parameter.

Additional exceptions:

If I change condition to Convert.ToInt32(CurrentUser.CurrentTeamType) == 1, I get the following exception Expression of type 'Namespace.TeamType' cannot be used for parameter of type 'System.Object' of method 'Int32 ToInt32(System.Object)'

If I change condition to (int)CurrentUser.CurrentTeamType == 1, I get the following exception Unknown identifier 'int'

If I add namespace too like var condition = "CurrentUser.CurrentTeamType == App.BE.TeamType.Admin";, I get Unknown identifier 'App'. Please note that I have a reference to App.BE namespace

score 1 · Accepted Answer · edited May 23 '17 at 12:15

1

Try using the full namespace to TeamType. Since you are using it in a string, it probably just needs you to be more specific.

UPDATE:

I think this answer will help you. You need to set up predefined types ahead of time.

edited May 23 '17 at 12:15

Community

1
1

answered Jan 18 '16 at 17:20

Dan Friedman

4,941
2
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I've tried that in the first. I will update my question – Alexandru Chichinete Jan 18 '16 at 17:21
A reference in the class is meaningless, because you are sending in a string. Use the full namespace as if there are no 'using' statements. – Dan Friedman Jan 18 '16 at 17:42
Updated my question. I've done that but only posted `BE` instead `App.BE` – Alexandru Chichinete Jan 18 '16 at 17:45
You need to be super clear here, since we can't see all your code. So if you put `App.BE` in, the error still says `BE` is the problem? Is `App.BE` added as a reference in your project? If you typed `App.BE` in the above method, does it resolve? If not, you are missing a needed project reference. – Dan Friedman Jan 18 '16 at 17:52
As i said in question, references are ok. If i type App.BE i see intelisense for it. – Alexandru Chichinete Jan 18 '16 at 18:02
Thanks for leading me to that question – Alexandru Chichinete Jan 19 '16 at 09:51

score 0 · Answer 2 · answered Feb 01 '16 at 20:49

0

There is much easier solution - just use text representation of enum value, i.e. this will work:

var condition = "CurrentUser.CurrentTeamType == \"Admin\"";

answered Feb 01 '16 at 20:49

creo

49
6

Pass an Enum as parameter in DynamicExpression

2 Answers2