Error - Cannot convert system.date.time? to system.date.time

Since the type of the objResult variable is already clear from the method name (GetSessionDeliveryParticipantList), you can use the var keyword to simplify the code

var objResult = bALSessionDeliveryParticipant.GetSessionDeliveryParticipantList(startDate, endDate, mentor, group);

 Instead of using the ternary operator to check for null values and set a default value, you can use the null-coalescing operator (??) to provide a default value if the StartDate or EndDate properties are null
 
 

 DateTime startDate = Result.StartDate ?? DateTime.MinValue;
DateTime endDate = Result.EndDate ?? DateTime.MaxValue;

Hi,

You are getting null value from database query response for datefield which is not nullable so it will throw error. 

You can solve this problem in multiple ways,

1. You can return default values from your query.
2. If you have nullable field in table then you can create nullabale filed in your viewmodel where you are storing result. If you create date field nullable with ? Then it will resolve.

You can add ? In your model as below

Public Datetime? StartDate {get; set;}