How to change Mapping for all Indices & for all Types at once

Hello All,

I am trying to change the mapping for the below 3 indices/types I have:



I am trying to follow the info given in the link:

$ curl -XPUT 'http://localhost:9200/rss/feeds/_mapping' -d '{"feeds" :
{"properties" : {"_all" : {"type" : "string", "store" : "yes"}}}}'
Result : {"ok":true,"acknowledged":true} - (I am able to change the mapping
for the index rss of type feeds)

but If I want to change all of the indices and types at once and tried:
$ curl -XPUT 'http://localhost:9200/_all/_mapping' -d '{"_all" :
{"properties" : {"_all" : {"type" : "string", "store" : "yes"}}}}'

{"error":"ActionRequestValidationException[Validation Failed: 1: mapping
type is missing;]","status":500}

curl -XPUT 'http://localhost:9200/_all/_mapping' -d '{"TYPE??????" :
{"properties" : {"_all" : {"type" : "string", "store" : "yes"}}}}'
so How to make this work ? What will be type ??

*The reson why I wanted to change the Mapping: *

I am Using NEST(.NET API)

I am able to index the objects pretty well, but now when I tried to
serialize the object using Json converter and index the string object(c#
code excutes fine but... I get the following error in ElasticSearch Server:)
Failed to excute [index { so n so..., Source so n so...]
org.elasticsearch.index.mapper.MapperParsingException: Malformed content,
must start with an object*

Any help will be much appreciated.