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Compiler Error CS1922

Collection initializer requires its type 'type' to implement System.Collections.IEnumerable.

In order to use a collection initializer with a type, the type must implement IEnumerable. This error can occur if you accidentally use collection initializer syntax when you meant to use an object initializer.

To correct this error

  • If the type does not represent a collection, use object initializer syntax instead of collection initializer syntax.

  • If the type does represent a collection, modify it to implement IEnumerable before you can use collection initializers to initialize objects of that type.

  • If the type represents a collection and you do not have access to the source code, just initialize its elements by using their class constructors or other initialization methods.


The following code produces CS1922:

// cs1922.cs
public class Test
    public static void Main()
        // Collection initializer.
        var tc = new TestClass  {1,"hello"} ; // CS1922

        // Object initalizer.
        var tc2 = new TestClass { memberA = 1, memberB = "hello" }; // OK

public class TestClass
    public int memberA { get; set; }
    public string memberB { get; set; }

See Also


Object and Collection Initializers (C# Programming Guide)