Linq / EF in ASP.NET Blazor - entity-framework

Question

I am using Blazor.
I am trying to get a specific result from dbset.
I have two conditions, salary is 620 and deduction is for p2.
The difficult thing is range, btw 600~700 for salary. Then how I move to specific column to get the result for p2.
var result = await _db.TaxTable.......blah...blah...
In this case, I have to find the result 70
I have tried some code..but I failed everytime.
Could you share the exact knowledge?
Thank you in adv.

Answer 1

You have to locate the row. Then use a switch statement to get the appropriate value.
double GetDeduction(double salary, string discount)
{
var row = someData.SingleOrDefault(a => salary >= a.start && salary < a.end);
if(row == null) throw new SomeRowNotFoundException();
return discount switch
{
"p1" => row.p1,
"p2" => row.p2,
"p3" => row.p3,
_ => throw new SomeDiscountNotValidException();
}
}
You have to include one of the boundaries and exclude the other to avoid overlap. I arbitrarily chose to include start the alternative would be
someData.SingleOrDefault(a => salary > a.start && salary <= a.end)

Answer 2

Your query into your DbSet should look something like this to get the specific value:
using var dbContext = _factory.CreateDbContext();
dbContext.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;
var value = await dbContext.Set<TRecord>()
.SingleOrDefault(item => item.start <= this.salary && item.end >= this.salary)?.p2 ?? 0;
Here's a demo page.
#page "/"
<PageTitle>Index</PageTitle>
<input class="form-control" #bind-value=this.salary />
<div class="text-end m-2">
<button class="btn btn-primary" #onclick=Calc>Calculate</button>
<button class="btn btn-secondary" #onclick=Calc2>Calculate 2</button>
</div>
<div class="bg-dark text-white m-2 p-2">
P2 = #P2
</div>
#code {
private int salary;
private int P2;
private void Calc()
{
var record = deductions.SingleOrDefault(item => item.start <= this.salary && item.end >= this.salary);
P2 = record?.p2 ?? 0;
}
private void Calc2()
{
P2 = deductions.SingleOrDefault(item => item.start <= this.salary && item.end >= this.salary)?.p2 ?? 0;
}
private List<Deduction> deductions = new List<Deduction>
{
new Deduction(1,0,199,10,20,30),
new Deduction(2,200,299,20,30,40),
new Deduction(3,300,399,30,40,50),
new Deduction(4,400,499,40,50,60),
};
public record Deduction(int Id, int start, int end, int p1, int p2, int p3 );
}
Note: there's a problem in your dataset your ranges overlap!