Login Authentication error while connecting to SQL Server using ASP.NET MVC

While connecting to SQL Server using Dapper ORM, I'm getting this error:

Login failed for user 'ttest'.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.SqlClient.SqlException: Login failed for user 'ttest'.

Source Error:

Line 40: using (SqlConnection sqlCon = new SqlConnection(connectionString))
Line 41: {
Line 42: sqlCon.Open();
Line 43: return sqlCon.Query(procedureName, param, commandType: CommandType.StoredProcedure);
Line 44: }

Line 42 is shown as an error

Code is

using Dapper;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.SqlClient;
using System.Data;

namespace DapperMVC.Models
{
    public class DapperORM
    {
        private static string connectionString = @"Data Source = test01\itest;Initial Catalog = SubbuDB; Persist Security Info=True;User ID = esiinttest; Password=***********;";

        public static void ExecuteWithoutReturn(string procedureName, DynamicParameters param = null)
        {
            using (SqlConnection sqlCon = new SqlConnection(connectionString))
            {
                sqlCon.Open();
                sqlCon.Execute(procedureName, param, commandType: CommandType.StoredProcedure);
            }
        }

        //DapperORM.ExecuteReturnScalar<int>(_,_);
        public static T ExecuteReturnScalar<T>(string procedureName, DynamicParameters param = null)
        {
            using (SqlConnection sqlCon = new SqlConnection(connectionString))
            {
                sqlCon.Open();
                return (T)Convert.ChangeType(sqlCon.ExecuteScalar(procedureName, param, commandType: CommandType.StoredProcedure), typeof(T));
            }
        }

        //DapperORM.ReturnList<EmployeeModel> <=  IEnumerable<EmployeeModel>
        public static IEnumerable<T> ReturnList<T>(string procedureName, DynamicParameters param = null)
        {
            using (SqlConnection sqlCon = new SqlConnection(connectionString))
            {
                sqlCon.Open();
                return sqlCon.Query<T>(procedureName, param, commandType: CommandType.StoredProcedure);
            }
        }
    }
}