Hi skp,

Check this example. Now please take its reference and correct your code.

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

Here i have used SplitString function. You can refer below article for more details.

Split and convert Comma Separated (Delimited) String to Table in SQL Server

HTML

<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.5.5/angular.js"></script>
<script type="text/javascript">
    var app = angular.module("MyApp", []);
    app.controller("MyController", function ($scope, $http) {
        $scope.Cities = [{ Name: "Kirkland" }, { Name: "London" },
                        { Name: "Redmond" }, { Name: "Seattle" }, { Name: "Tacoma"}];
        $scope.Search = function () {
            var cities = [];
            for (var i = 0; i < $scope.Cities.length; i++) {
                if ($scope.Cities[i].hasChecked) {
                    cities.push($scope.Cities[i].Name);
                }
            }

            $http.post("Default.aspx/GetEmployees", JSON.stringify({ cities: cities }), {
                headers: { 'Content-Type': 'application/json' }
            }).then(function (response) {
                $scope.Employees = eval(response.data.d);
            });
        }
    });
</script>
<div ng-app="MyApp" ng-controller="MyController">
    <table>
        <tr ng-repeat="city in Cities">
            <td><input type="checkbox" ng-change="Search()" ng-model="city.hasChecked" /></td>
            <td style="padding-left: 5px">{{city.Name}}</td>
        </tr>
    </table>
    <br />
    <table>
        <tr>
            <th>Id</th>
            <th>Name</th>
            <th>City</th>
        </tr>
        <tr ng-repeat="employee in Employees">
            <td>{{employee.EmployeeId}}</td>
            <td>{{employee.Name}}</td>
            <td>{{employee.City}}</td>
        </tr>
    </table>
</div>

Namespaces

C#

using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web.Services;
using Newtonsoft.Json;

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.Services
Imports Newtonsoft.Json

Code

C#

[WebMethod]
public static string GetEmployees(string[] cities)
{
    string jsonString = "";
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    string query = "SELECT EmployeeId,FirstName+' '+LastName Name,City FROM Employees WHERE City IN (SELECT Item FROM dbo.SplitString(@Cities, ','))";
    SqlCommand cmd = new SqlCommand(query);
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            cmd.Parameters.AddWithValue("@Cities", string.Join(",", cities));
            sda.SelectCommand = cmd;
            using (DataTable dt = new DataTable())
            {
                sda.Fill(dt);
                jsonString = JsonConvert.SerializeObject(dt);
            }
        }
    }

    return jsonString;
}

VB.Net

<WebMethod()> _
Public Shared Function GetEmployees(ByVal cities As String()) As String
    Dim jsonString As String = ""
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Dim query As String = "SELECT EmployeeId,FirstName+' '+LastName Name,City FROM Employees WHERE City IN (SELECT Item FROM dbo.SplitString(@Cities, ','))"
    Dim cmd As SqlCommand = New SqlCommand(query)
    Using con As SqlConnection = New SqlConnection(conString)
        Using sda As SqlDataAdapter = New SqlDataAdapter()
            cmd.Connection = con
            cmd.Parameters.AddWithValue("@Cities", String.Join(",", cities))
            sda.SelectCommand = cmd
            Using dt As DataTable = New DataTable()
                sda.Fill(dt)
                jsonString = JsonConvert.SerializeObject(dt)
            End Using
        End Using
    End Using

    Return jsonString
End Function

Screenshot