C# Lambda Expression translated strange, Any Suggestions?

I have problem with the following lambda expression:

public IEnumerable<ModuleEntity> GetPageList(Pagination pagi, string query)
{
    var expression = LinqExpression.Default<ModuleEntity>();
    expression = expression.And(e =>
       e.DeleteMark != 1 &&
       e.EnableMark != 0
    );

   return this.BaseRepository().GetList(expression, pagi);
}

This is my code, I want to add default expression to my business. Note: the properties EnableMark and DeleteMark are nullable<int>. When I debug, the lambda expression translate the expression to this:

{p => ((1 == 1) AndAlso ((p.DeleteMark != Convert(1)) AndAlso (p.EnableMark != Convert(0))))};

It leads to my Query throwing an exception:

// use Dapper connection Query
var query = dbConnection.Query<T>(linq);

Exception: Unrecognized NodeType (Convert),

I can't figure out why the lambda expression gives me Covnert(1) and Convert(0), any suggestions?

I tried to change the property EnableMark and DeleteMark to int instead of nullable<int>, then it worked. But in the other cases, nullable type is necessary, is there any solutions or documents ? Thanks.

@Eric Lippert Thank you for pointing out the causes, I set a variable of value '1', let it's type to int?, and assigned to DeleteMark. It worked !!

public IEnumerable<ModuleEntity> GetPageList(Pagination pagi, string query)
{
    var expression = LinqExpression.Default<ModuleEntity>();
    int? deleteMark = 1;
    int? enableMark = 0
    expression = expression.And(e =>
       e.DeleteMark != deleteMark &&
       e.EnableMark != enableMark
    );

   return this.BaseRepository().GetList(expression, pagi);
}