无法加载文件或程序集'System.ValueTuple，版本= 4.0.3.0，

Question

我正在一个asp.net c＃应用程序上与Postgresql连接。我有Windows 7 32位的PC。 首先，我在PC上安装了Postgresql版本 postgresql-10.14-1-windows 。然后我试图从C＃窗口应用程序将数据插入到postgresql中。为此，我在项目中添加了“ Npgsql.dll”和“ System.ValueTuple.dll”的引用，并尝试了以下代码

var cs = "Host=localhost;Username=testuser;Password=test12345;Database=test;";
            using (NpgsqlConnection connection = new NpgsqlConnection(cs))
            {
                
                //connection.ConnectionString = ConfigurationManager.ConnectionStrings["constr"].ToString();
                //connection.ConnectionString = cs;
                connection.Open();
                NpgsqlCommand cmd = new NpgsqlCommand();
                cmd.Connection = connection;
                cmd.CommandText = "Insert into employee values(@ID,@Fname,@Lname,@Email)";
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.Add(new NpgsqlParameter("@ID", Convert.ToInt32(txtEmpID.Text)));
                cmd.Parameters.Add(new NpgsqlParameter("@EmpName", txtEmpName.Text));
                cmd.Parameters.Add(new NpgsqlParameter("@Email", txtEmpEmail.Text));
                cmd.Parameters.Add(new NpgsqlParameter("@Phone", txtEmpPhone.Text));
                cmd.ExecuteNonQuery();
                cmd.Dispose();
                connection.Close();
                txtEmpEmail.Text = "";
                txtEmpName.Text = "";
                txtEmpID.Text = "";
                txtEmpPhone.Text = "";
                lblmsg.Text = "Data Has been Saved";
            }

但是当我尝试运行它时会提示错误

{"Could not load file or assembly 'System.ValueTuple, Version=4.0.3.0, Culture=neutral, 
 PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The located assembly's manifest definition does not 
 match the assembly reference. (Exception from HRESULT: 0x80131040)":"System.ValueTuple, Version=4.0.3.0, 
 Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51"}

位置

 using (NpgsqlConnection connection = new NpgsqlConnection(cs))

我尝试了很多解决方法，但是我对Postgresql还是很陌生，无法找到解决方案。请在这里帮助我。