Form Collection Handling

4/22/26Less than 1 minute

Form Collection Handling

According to OpenAPI specification, collections in URI query or form fields support 5 representation formats:

Format	Description
Csv	Comma-separated
Ssv	Space-separated
Tsv	Backslash-separated
Pipes	Pipe-separated
Multi	Multiple key-value pairs with the same name

Example

For an array value like id = ["001", "002"], when processed by PathQueryAttribute or FormContentAttribute:

CollectionFormat	Data
`[PathQuery(CollectionFormat = CollectionFormat.Csv)]`	`id=001,002`
`[PathQuery(CollectionFormat = CollectionFormat.Ssv)]`	`id=001 002`
`[PathQuery(CollectionFormat = CollectionFormat.Tsv)]`	`id=001\002`
`[PathQuery(CollectionFormat = CollectionFormat.Pipes)]`	`id=001\|002`
`[PathQuery(CollectionFormat = CollectionFormat.Multi)]`	`id=001&id=002`

Usage Example

public interface IUserApi
{
    [HttpGet("api/users")]
    Task<List<User>> GetAsync(
        [PathQuery(CollectionFormat = CollectionFormat.Multi)] int[] ids);
}

Resulting request: api/users?ids=1&ids=2&ids=3