Getting error while consuming Web API in Xamarin forms cross platform - asp.net-web-api

Question

Getting below error while consuming web API in Xamarin forms "Cannot convert from Login to System.Net.Http.HttpCompletionOption"
I'm new to mobile development ,please help me in completing the above code for consuming the API's in Xamarin cross platform.
Below is the code for WEB API
public class DBLoginController : ApiController
{
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["db_test"].ConnectionString);
SqlCommand cmd = new SqlCommand();
SqlDataAdapter adp = null;
[HttpGet]
[ActionName("getCustomerInfo")]
public DataTable Get()
{
DataTable dt = new DataTable();
try
{
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select * from tbl_admin";
cmd.Connection = con;
if (con.State == ConnectionState.Open)
{
con.Close();
}
adp = new SqlDataAdapter(cmd);
dt.TableName = "tbl_admin";
adp.Fill(dt);
con.Close();
}
catch
{
}
return dt;
}
[HttpPost]
public int Login([System.Web.Http.FromBody] Login lgn)
{
int ret = 0;
try
{
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select count(*) from tbl_admin where username='"+lgn.username+"'username and password='"+ lgn.password + "'";
cmd.Connection = con;
if (con.State == ConnectionState.Open)
{
con.Close();
}
con.Open();
ret = Convert.ToInt32(cmd.ExecuteScalar());
con.Close();
}
catch
{
}
return ret;
}
}
Below is the code for consuming API in xamarin form
private async void BtnLogin_Clicked(object sender, EventArgs e)
{
var client = new HttpClient();
client.BaseAddress = new Uri("http://********.com/api/DBLogin/getCustomer");
Login lgn = new Login { username = txtUsername.Text.ToString(), password = txtPassword.Text.ToString() };
var response = client.GetAsync("api/Login/Login").Result;
var a = response.Content.ReadAsStringAsync();
if (a.Result.ToString().Trim() == "0")
{
messageLabel.Text = "Invalid login credentials.";
}
else
{
await Navigation.PushModalAsync(new Page2());
}
}
}
}
please help
Thanks in advance