Compiler Error CS0745

  • Article

Expected contextual keyword 'by'

The pattern for the group clause is group...by followed by an optional into, as shown in the following example:

string[] names = { "Bob", "Bill", "Jonetta", "Mary" };

var query = from name in names
            group name by name[0];

or

var query2 = from name in names
             group name by name[0] into g
             //...additional query clauses

To correct this error

  • Add the by keyword to the group clause.

Example

The following code generates CS0745:

// cs0745.cs
using System;
using System.Linq;

public class C
{
    public static int Main()
    {
        string[] names = { "Bob", "Bill", "Jonetta", "Mary" };

        var query = from name in names
                    group name name[0]; // CS0745
                
        return 1;
    }
}

See Also

Concepts

LINQ Query Expressions (C# Programming Guide)

Reference

group clause (C# Reference)