How to send a list of int from Javascript (Ajax) to C#?

A list in JavaScript looks like:

var list = [ 1, 2, 3, 4 ];

To build it you can do:

var list = [];
list.push(1);
list.push(2);
list.push(3);
list.push(4);

Then when you send it you can do:

$.ajax({
    url: '@Url.Action("PlantHistoryContent", "PlantStatus")',
    data: { ids: list },
    async: false,
    type: "POST"
})

or

$.ajax({
    url: '@Url.Action("PlantHistoryContent", "PlantStatus")',
    data: { ids: [ 1, 2, 3, 4 ] },
    async: false,
    type: "POST"
})

By default form-encoding is used. The request body will look like:

ids[0]=1&ids[1]=2&ids[2]=2&ids[3]=3

With form-encoding there is no way to know what the type of the parameter is. They're all strings.

If you use JSON as your transfer encoding instead you can send integers because JSON knows string and ints and list etc.

$.ajax({
    url: '@Url.Action("PlantHistoryContent", "PlantStatus")',
    data: { data: JSON.stringify({ ids: [ 1, 2, 3, 4 ] }) },
    async: false,
    type: "POST"
})

Now your request body looks like:

data=%5B1%2C2%2C3%2C4%5D

For some one who may searching same problem like above. If you still cannot find any idea from other answers. I got the same issue, and here is my solution: just simple add [FromBody] to controller action

public void PlantHistoryContent([FromBody]List<int> id)
{
    //
}