# Merge Multiple Excel Files Posted from Client
## Content
This section demonstrates how to call the Web API service through a client application and merge multiple excel files, that are posted from client, into workbook.
[Step 1: Call the Service](/componentone/docs/webapi/online-webapi/Services/ExcelServices/MergeExcelService/POSTMergeExcel#step-1-call-the-service)
[Step 2: Run the Client Project](/componentone/docs/webapi/online-webapi/Services/ExcelServices/MergeExcelService/POSTMergeExcel#step-2-run-the-client-project)
The following example makes a call to the Web API [service](/componentone/docs/webapi/online-webapi/overview/WorkingwithC1WebAPI/ConfiguringWebAPI) through HTML as well as WinForms client applications. These clients send a POST request to the service, which returns a response stream. This response stream is then saved in the desired excel file format.
In the following example, user provides the excel files (to merge into workbook) through the client applications. Moreover, the end user needs to specify the service URL, name and desired file format of workbook (generated upon merging multiple excel sheets) through client project. It is so, because the parameters or query string for merging excel are sent in the HTTP message body of the POST request and not in the request URL.
>type=note
> **Note**: Service can merge xls, xlsx, and csv files posted from the client.
### Step 1: Call the Service
Complete the following steps to call the Web API service.
**csharp**
```csharpC#
private void button1_Click(object sender, EventArgs e) {
OpenFileDialog x = new OpenFileDialog();
x.Multiselect = true;
x.ShowDialog();
result = x.FileNames;
label1.Text = "Files Selected";
}
```
**HTML**
1\. Create an HTML application\, as discussed in [Configure Client for REST API service](/componentone/docs/webapi/online-webapi/overview/WorkingwithC1WebAPI/configuring-the-client-application/ClientAppRESTApiServices).
2. Add the following markups in the \
```
Note that, for POST request we set **method** attribute of \