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Add example showing difference between directly toList or using IQueryable.

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This commit is contained in:
Kevin Matsubara 2025-04-05 21:48:12 +02:00
parent 1aae643a78
commit 915434f44d
1 changed files with 45 additions and 0 deletions
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45
EntityFrameworkCore.Console/Program.cs
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@ -1,4 +1,5 @@
using EntityFrameworkCore.Data;
using EntityFrameworkCore.Domain;
using Microsoft.EntityFrameworkCore;
using var context = new DeadBallZoneLeagueDbContext();
@ -14,6 +15,50 @@ var teamFour = await context.Teams.SingleOrDefaultAsync(t => t.TeamId == 3);
// Rather than raise: "System.InvalidOperationException: Sequence contains no elements."
var coach = await context.Coaches.FirstOrDefaultAsync();
await ListVSIQueryableCall();
async Task ListVSIQueryableCall()
{
Console.WriteLine("Enter '1' for team with Id 1 or enter '2' for teams that contain 'Neo'");
var option = Convert.ToInt32(Console.ReadLine());
List<Team> teamsAsList = new List<Team>();
// After executing ToList, the records are stored in memory.
// Operations after that, are also done in memory.
teamsAsList = await context.Teams.ToListAsync();
if (option == 1)
{
teamsAsList = teamsAsList.Where(t => t.TeamId == 1).ToList();
}
else if (option == 2)
{
teamsAsList = teamsAsList.Where(t => t.Name.Contains("Neo")).ToList();
}
foreach (var team in teamsAsList)
{
Console.WriteLine(team.Name);
}
// Records stay as IQueryable until the ToList function is called, then the final query is performed.
var teamsAsQueryable = context.Teams.AsQueryable();
if (option == 1)
{
teamsAsQueryable = teamsAsQueryable.Where(t => t.TeamId == 1);
}
else if (option == 2)
{
teamsAsQueryable = teamsAsQueryable.Where(t => t.Name.Contains("Neo"));
}
// the actual query:
teamsAsList = await teamsAsQueryable.ToListAsync();
foreach (var team in teamsAsList)
{
Console.WriteLine(team.Name);
}
}
async Task TrackedQuery()
{
// EF Core tracks objects that are returned by queries.