无法将类型“ System.DateTime”隐式转换为“ LearnScan.LearnUser.NullableDateTime”

Question

Trying to set a value for a create user soap call and when setting a startdate for a new user:

DateTime? dt = DateTime.Now;
emptyUsr.StartDate = dt;

It returns an error of "Cannot implicitly convert type 'System.DateTime' to 'LearnScan.LearnUser.NullableDateTime'" I was under the impression that DateTime? sets to nullable?

The StartDate property has type LearnScan.LearnUser.NullableDateTime which is defined as:

public partial class NullableDateTime : object, System.ComponentModel.INotifyPropertyChanged {
    internal static object DateTime;
    private bool isNullField;

    private System.DateTime valueField;

    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute(Order=0)]
    public bool IsNull {
        get {
            return this.isNullField;
        }
        set {
            this.isNullField = value;
            this.RaisePropertyChanged("IsNull");
        }
    }

    /// <remarks/>
    [System.Xml.Serialization.XmlElementAttribute(Order=1)]
    public System.DateTime Value {
        get {
            return this.valueField;
        }
        set {
            this.valueField = value;
            this.RaisePropertyChanged("Value");
        }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChanged(string propertyName) {
        System.ComponentModel.PropertyChangedEventHandler propertyChanged = this.PropertyChanged;
        if ((propertyChanged != null)) {
            propertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }
}

*Solution - It wanted values for each emptyUsr.StartDate.IsNull = false and emptyUsr.StartDate.Value= DateTime.Now;

Answer 1

You can create an implicit conversion from DateTime? to your NullableDateTime class:

namespace LearnScan.LearnUser {
    public partial class NullableDateTime
    {
        public static implicit operator NullableDateTime(DateTime? dt)
        {
            if(dt.HasValue)
            {
                return new NullableDateTime { IsNull = false, Value = dt.Value };
            }
            else
            {
                 return new NullableDateTime { IsNull = true };
            }
        }
    }
}

Answer 2

The NullableDateTime externally-defined type (since that is not part of the regular C# set of libraries and APIs) is not the same as DateTime? . Although its short name might trick you into thinking that, its full name LearnScan.LearnUser.NullableDateTime tells you that it is very different from System.DateTime? (which is the actual full name of DateTime? in .NET). You need to understand how NullableDateTime was implemented and how to use it. It might be a different approach to a nullable DateTime type built upon the DateTime struct .NET offers, as of the short snippet you provided in the comments.