wpf 实现IDataErrorInfo

publicclass Contact : IDataErrorInfo
{
    privatestring _firstName;
    privatestring _lastName;

    publicstring FirstName
    {
        get { return _firstName; }
        set { _firstName = value; }
    }

    publicstring LastName
    {
        get { return _lastName; }
        set { _lastName = value; }
    }

    #region IDataErrorInfo Memberspublicstring Error
    {
        get { thrownew NotImplementedException(); }
    }

    publicstringthis[string columnName]
    {
        get 
        {
            string result =null;

            if( columnName =="FirstName" )
            {
                if (String.IsNullOrEmpty( FirstName) )
                    result ="Firstname has to be set!";
                elseif (FirstName.Length <5)
                    result ="Firstname's length has to be at least 5 characters!";
            }
            elseif (columnName =="LastName")
            {
                if (String.IsNullOrEmpty(LastName))
                    result ="LastName has to be set!";
                elseif (LastName.Length <5)
                    result ="LastName's length has to be at least 5 characters!";
            }

            return result;
        }
    }

    #endregion
}