c# - 使用 DAL BLL 函数的 Windows 窗体不显示对象

Question

我的 EmployeeDB 类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Data;

namespace Test
{
    public class EmployeeDB
    {
        private string connectionString;

        public EmployeeDB()
        {
            //my connectionstring info
        }

        public int CountEmployees()
        {
            SqlConnection con = new SqlConnection(connectionString);
            SqlCommand cmd = new SqlCommand("CountEmployees", con);
            cmd.CommandType = CommandType.StoredProcedure;

            try
            {
                con.Open();
                return (int)cmd.ExecuteScalar();
            }
            catch (SqlException err)
            {
                // Replace the error with something less specific.
                // You could also log the error now.
                throw new ApplicationException("Data error.");
            }
            finally
            {
                con.Close();
            }
        }

        public List<EmployeeDetails> GetEmployees()
        {
            SqlConnection con = new SqlConnection(connectionString);
            SqlCommand cmd = new SqlCommand("GetAllEmployees", con);
            cmd.CommandType = CommandType.StoredProcedure;

            // Create a collection for all the employee records.
            List<EmployeeDetails> employees = new List<EmployeeDetails>();

            try
            {
                con.Open();
                SqlDataReader reader = cmd.ExecuteReader();

                while (reader.Read())
                {
                    EmployeeDetails emp = new EmployeeDetails(
                        (int)reader["EmployeeID"], (string)reader["FirstName"],
                        (string)reader["LastName"], (string)reader["TitleOfCourtesy"]);
                    employees.Add(emp);
                }
                reader.Close();

                return employees;
            }
            catch (SqlException err)
            {
                // Replace the error with something less specific.
                // You could also log the error now.
                throw new ApplicationException("Data error.");
            }
            finally
            {
                con.Close();
            }
        }
    }
}

我的员工详细信息类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace Test
{
    public class EmployeeDetails
    {
private int employeeID;
        private string firstName;
        private string lastName;
        private string titleOfCourtesy;

        public int EmployeeID
        {
            get {return employeeID;}
            set {employeeID = value;}
        }
        public string FirstName
        {
            get {return firstName;}
            set {firstName = value;}
        }
        public string LastName
        {
            get {return lastName;}
            set {lastName = value;}
        }
        public string TitleOfCourtesy
        {
            get {return titleOfCourtesy;}
            set {titleOfCourtesy = value;}
        }

        public EmployeeDetails(int employeeID, string firstName, string lastName,
            string titleOfCourtesy)
        {
            this.employeeID = employeeID;
            this.firstName = firstName;
            this.lastName = lastName;
            this.titleOfCourtesy = titleOfCourtesy;
        }

        public EmployeeDetails(){}

    }
}

当我构建类库并将引用添加到我的 windows 窗体项目时。

这是该课程显示的主要表格的屏幕截图；但是，没有方法。

Answer 1

要绑定到 DataGrid：

1. 在表单中添加一个 BindingSource (bindingSource)
2. 将 DataGrid 的 DataSource 属性设置为 bindingSource
3. 将 bindingSource 的 DataSource 属性设置为 GetEmployees() 的结果

如果您的库具有以下实现，例如：

public interface IDataOperation
{
    List<Employee> GetEmployees();
}

public class DataOperation : IDataOperation
{
    public List<Employee> GetEmployees(){}
}

您的实现应如下所示：

IDataOperation dataOperation = new DataOperation();

var bindingSource = new BindingSource();
dataGrid.DataSource = bindingSource;
bindingSource.DataSource = dataOperation.GetEmployees();

或者，您可以直接以编程方式将 DataGrid 的 DataSource 属性设置为 GetEmployees() 的结果，而不使用 BindingSource：

dataGrid.DataSource = dataOperation.GetEmployees();

编辑：在您的屏幕截图中，您应该在使用它之前实例化您的 EmployeeDB，如下面的代码：

Test.EmployeeDB employeeDB = new Test.EmployeeDB();
dataGrid.DataSource = employeeDB.GetEmployees(); // assuming you have a dataGrid control