通过在Web API控制器中添加配置解决连接问题。

在Web API控制器中添加以下配置代码：

using System.Data.SqlClient;
using System.Configuration;
using System.Web.Http;
using System.Web.Http.Cors;

namespace YourApplication.Controllers
{
    // Enable CORS
    [EnableCors(origins: "*", headers: "*", methods: "*")]
    public class YourController : ApiController
    {
        // Connection string for SQL Server
        private readonly string connectionString = ConfigurationManager.ConnectionStrings["YourConnectionStringName"].ConnectionString;

        // GET: api/YourController
        public IEnumerable Get()
        {
            string query = "SELECT * FROM YourTable";
            var result = new List();

            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                SqlCommand command = new SqlCommand(query, connection);
                connection.Open();

                SqlDataReader reader = command.ExecuteReader();

                while (reader.Read())
                {
                    result.Add(reader.GetString(0)); // change to the desired column index
                }

                return result;
            }
        }
    }
}

确保在Web.config文件中添加正确的连接字符串：

重新建立您的应用程序后，您应该能够使用GET方法连接到SQL Server并检索数据。