Custom Attribute has a datetime property raises error

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I have a custom attribute class SoftwareAttribute where i need to set some string and datetime value.

C#

[AttributeUsage(AttributeTargets.All)]
    class SoftwareAttribute : Attribute
    {
        string projectName;
        DateTime startDate, endDate;
        public SoftwareAttribute(string pname, DateTime start, DateTime end)
        {
            projectName = pname;
            startDate = start;
            endDate = end;
        }
        public virtual string ProjectName
        {
            get { return projectName; }
            set { projectName = value; }
        }
      
        public virtual DateTime StartDate
        {
            get { return startDate; }
            set { startDate = value; }

        }
        public virtual DateTime EndDate
        {
            get { return endDate; }
            set { endDate = value; }
        }
    }

Now Payroll class is as follow

C#

[Software("Payroll ,new DateTime(2013,10,15), new DateTime(2013,11,10))]
    class Payroll
    {
    }

As i am trying to add 'new DateTime(2013,10,15)'. This statement raises error:-

'An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type'

How can i set datetime for startdate and enddate attribute from Payroll class.
And I don't want to use string for datetime.
Thank you.

Posted 15-Oct-13 5:26am

Brijesh Kr

Updated 15-Oct-13 17:41pm

v5

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Chris Ross 2 · Answer 1 · 2013-10-15T05:44:00

Unfortunately, as you've discovered, attributes won't allow you to supply as arguments values that must be allocated with new.

Which leaves you with having to make a compromise. Without knowing the larger context of the problem you're trying to solve with the attribute, what I would do in the situation is mae the start and end dates a string, not a DateTime.

Since you're capturing their values in the attribute's constructor, you can validate them in that constructor - and throw an exception if an invalid date string was supplied. Not the prettiest solution, but it scratches the itch.

Ravi Bhavnani · Answer 2 · 2013-10-15T07:28:00

Attribute parameters are restricted to constant values of the following types:

Simple types (bool, byte, char, short, int, long, float, and double)
string
System.Type
enums
object (The argument to an attribute parameter of type object must be a constant value of one of the above types.)
One-dimensional arrays of any of the above types

Replace your DateTime property with a string that is parsed at run time.

/ravi

Custom Attribute has a datetime property raises error

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