# Cannot convert lambda expression to type 'PostData' because it is not a delegate type
**URL:** https://discuss.elastic.co/t/cannot-convert-lambda-expression-to-type-postdata-because-it-is-not-a-delegate-type/138724
**Category:** Elasticsearch
**Created:** [July 5, 2018, 1:28pm UTC](https://discuss.elastic.co/t/cannot-convert-lambda-expression-to-type-postdata-because-it-is-not-a-delegate-type/138724 "2018-07-05T13:28:14Z")
**Posts on this page:** 8
**Page:** 1
I have this code in my .net core app
```
var searchResponse = client.Search(s => s
.From(0)
.Size(10)
.Query(q => q
.Match(m => m
.Field(f => f.FirstName)
.Query("Martijn")
)
)
```
);
which I got from this page [https://www.elastic.co/guide/en/elasticsearch/client/net-api/current/nest-getting-started.html](https://www.elastic.co/guide/en/elasticsearch/client/net-api/current/nest-getting-started.html)
I'm getting an error at design time "Cannot convert lambda expression to type 'PostData' because it is not a delegate type". I have referenced Elasticsearch and System.Linq.
What am I missing?
---
I've also tried this syntax from https://www.elastic.co/guide/en/elasticsearch/client/net-api/1.x/nest-quick-start.html
```
QueryContainer query = new TermQuery
```
{
Field = "firstName",
Value = "martijn"
};
var searchRequest = new SearchRequest
{
From = 0,
Size = 10,
Query = query
};
And now I get an error "cannot convert from 'Nest.SearchRequest' to 'Elasticsearch.Net.PostData"
I'm not sure why it is so hard to make a simple API call here.
---
Yes, they are both Version 6.2.0.
I've managed to use the ElasticLowLevelClient successfully to Index, but if I use that to Count or Search since it seems to just do a post, I can't map the response object to actually use the data I'm trying to get.
---
Ok. What is the type of `client` above? Would you be able to provide a short, but complete, example of the issue?
Also, would you be able to provide more details of the environment
- Windows, MacOS, Linux?
- framework TFM e.g. netcoreapp2.0
---
Hi, so this is embarrassing. I was wanting to use the Low Level Client, but that was obviously not right. I then tried adding the Nest reference and changing to High Level Client but that didn't work either.
Then I closed VS Code, reopened it and all of a sudden it works. Frustrating!
For info, in case anyone else has this -
Running on Windows
Elasticsearch v6.3.0 running locally (just for dev purposes)
Developing in C# (dotnet core), using VSCode.
Code now looks like:
```
var node = new Uri(Config.Configuration["elasticsearch:0:uri"]);
var settings = new ConnectionSettings( node );
Client = new ElasticClient(settings);
QueryContainer query = new MatchQuery
{
Field = keyValue.Key,
Query = keyValue.Value.ToString()
};
var searchRequest = new SearchRequest(index.IndexName, index.IndexType)
{
Query = query
};
var searchResults = Client.Search