拨打function里面linq查询

Question

I have list of object and i want to filter this to between to date.

I write function for this if date is between to dates return true else return false. This is my function.

private bool IsDateBetween(DateTime date, string min, string max) {
        bool resultMin = true;
        bool resultMax = true;
        if (!string.IsNullOrEmpty(min))
        {
            resultMin = date > Convert.ToDateTime(min);
        }
        if (!string.IsNullOrEmpty(max)) {
            resultMax = date < Convert.ToDateTime(max);
        }
        return resultMin&&resultMax;
    }

and this is how i call function with linq.

var policiesT = policies.Where(x=>IsDateBetween(x.StartofInsurance,startDateS,startDateF));

startDateS and startDateF is string of datetime and i checked that values.
They have value when i run the code.
But problem is when i debug the function min and max values always coming null. This is the image before the calling function This is the image when function is running. Why that values caming null can u helpp me.
Thanks

Answer 1

This maybe not an answer but in comments would be a mess. This sample works fine for me:

void Main()
{
    var policies = new List<Policy> {
        new Policy {StartofInsurance=new DateTime(2021,1,1)},
        new Policy {StartofInsurance=new DateTime(2021,6,21)},
        new Policy {StartofInsurance=new DateTime(2021,7,13)},
    };
    string startDateS = "01/09/2021";
    string startDateF = "07/01/2021";
    var policiesT = policies.Where(x => IsDateBetween(x.StartofInsurance, startDateS, startDateF));
    foreach (var p in policiesT)
    {
        Console.WriteLine(p.StartofInsurance);
    }
}

private bool IsDateBetween(DateTime date, string min, string max)
{
    bool resultMin = true;
    bool resultMax = true;
    if (!string.IsNullOrEmpty(min))
    {
        resultMin = date > Convert.ToDateTime(min);
    }
    if (!string.IsNullOrEmpty(max))
    {
        resultMax = date < Convert.ToDateTime(max);
    }
    return resultMin && resultMax;
}

public class Policy
{
    public DateTime StartofInsurance { get; set; }
}

And returns the correct policy:

6/21/2021 12:00:00 AM