C#•2y ago

❔ Predicate in LINQ GroupBy

Hello, how can I replace item.Name with the predicate?

public static ObservableCollection<GroupInfo> Create<TData>(IEnumerable<TData> data, Expression<Func<TData, string>> predicate)
    where TData : class
{
    IEnumerable<GroupInfo> query = data
        .GroupBy(item => item.Name.ToUpper())
        .OrderBy(g => g.Key)
        .Select(g => new GroupInfo(g.Key, g));

    return new ObservableCollection<GroupInfo>(query);
}

public static ObservableCollection<GroupInfo> Create<TData>(IEnumerable<TData> data, Expression<Func<TData, string>> predicate)
    where TData : class
{
    IEnumerable<GroupInfo> query = data
        .GroupBy(item => item.Name.ToUpper())
        .OrderBy(g => g.Key)
        .Select(g => new GroupInfo(g.Key, g));

    return new ObservableCollection<GroupInfo>(query);
}

14 Replies

Halfbax•2y ago

I have tried to replace it with .GroupBy(item => predicate.ToUpper()), but the result is x instead of the string inside of item.Name.

Anton•2y ago

predicate(item).ToUpper() why is it an expression? ef core?

Thinker•2y ago

Also regular IEnumerable<T> doesn't operate on Expression (?) Only IQueryable<T> operates on Expressions

Halfbax•2y ago

I have copied it from my generic ef methods. Seems to be a mistake

Anton•2y ago

use iqueryable you also need expression expanding I don't know how this works, but there's a package I know that could help LinqKit

Halfbax•2y ago

This works?

Anton•2y ago

pretty sure no

Thinker•2y ago

If it's not an Expression, it will work

Anton•2y ago

but it's not gonna run on the db if you convert the query to ienumerable

Halfbax•2y ago

It wont run on ef I just want to convert and sort my current list It works Thanks for the help 🙂 If I convert it to iqueryable do I have to use the linqkit?

Anton•2y ago

you use it to expand the expressions without that library it's nastier

Halfbax•2y ago

ah kk thanks 🙂

Lexaro•2y ago

You can replace item.Name with the predicate argument

public static ObservableCollection<GroupInfo> Create<TData>(IEnumerable<TData> data, Expression<Func<TData, string>> predicate)
    where TData : class
{
    IEnumerable<GroupInfo> query = data
        .GroupBy(predicate.Compile()
                 .Invoke)
        .OrderBy(g => g.Key)
        .Select(g => new GroupInfo(g.Key, g));

    return new ObservableCollection<GroupInfo>(query);
}

public static ObservableCollection<GroupInfo> Create<TData>(IEnumerable<TData> data, Expression<Func<TData, string>> predicate)
    where TData : class
{
    IEnumerable<GroupInfo> query = data
        .GroupBy(predicate.Compile()
                 .Invoke)
        .OrderBy(g => g.Key)
        .Select(g => new GroupInfo(g.Key, g));

    return new ObservableCollection<GroupInfo>(query);
}

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Predicate in LINQ GroupBy