Cannot convert Task<List<TEntity>> to Task<IList<TEntity>>

user_5806893 0
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I'm writing a small wrapper method around EF Core DbSet. I have the following method:

public Task<IList<TEntity>> GetAsync(Func<IQueryable<TEntity>, IQueryable<TEntity>> getFunction)
{
    if (getFunction == null)
    {
        Task.FromResult(new List<TEntity>());
    }
    return getFunction(_dbSet).AsNoTracking().ToListAsync();
}

The class is generic as you can see and _dbSet is an instance of concrete DbSet from the context. It does not matter that much for the question, however.
For the code I get the below error:

[CS0029] Cannot implicitly convert type 'System.Threading.Tasks.Task>' to 'System.Threading.Tasks.Task>'

If I change return value to Task<List<TEntity>> there is no error.
Does anyone have an idea why it cannot convert it? Thanks!

async-await contravariance covariance asynchronous c#
1 Answers

The easiest way in my opinion is to await the task. So it will work with minimum changes:

public async Task<IList<TEntity>> GetAsync(Func<IQueryable<TEntity>, IQueryable<TEntity>> 
getFunction)
{
    if (getFunction == null)
    {
        return new List<TEntity>();
    }
    return await getFunction(_dbSet).AsNoTracking().ToListAsync();
}
user_46270310
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