如何实现以下要求：
-
检索按钮点击事件：
- 如果用户未在CCD_ 2中输入CCD_ 1，则需要通知用户通过CCD_
- 如果输入的CCD_ 4不存在于数据库中，则通过CCD_
- 更新按钮点击事件-需要确保数据库中已经存在客户ID
- 删除按钮点击事件：与检索按钮的要求相同
我必须使用错误/异常处理（try-catch）来实现这些（项目要求）。我花了几个小时尝试，但没有成功。如果能得到帮助，我将不胜感激！我的代码如下：
namespace ACME
{
public partial class Customer : System.Web.UI.Page
{
SqlConnection conn;
SqlDataAdapter adapter = new SqlDataAdapter();
DataTable table = new DataTable();
SqlCommand command = new SqlCommand();
protected void Page_Load(object sender, EventArgs e)
{
conn = new SqlConnection(ConfigurationManager.
ConnectionStrings["dbConnection1"].ConnectionString);
}
private void Page_PreInit(object sender, EventArgs e)
{
HttpCookie setTheme = Request.Cookies.Get("UserSelectedTheme");
if (setTheme != null)
{
Page.Theme = setTheme.Value;
}
}
protected void Clear()
{
txtCustID.Text = "";
txtFirstname.Text = "";
txtSurname.Text = "";
rbtGender.SelectedValue = "";
txtAge.Text = "";
txtAddress1.Text = "";
txtAddress2.Text = "";
txtCity.Text = "";
txtPhone.Text = "";
txtMobile.Text = "";
txtEmail.Text = "";
txtEmail2.Text = "";
}
protected void btnNew_Click(object sender, EventArgs e)
{
SqlDataAdapter adapter1 = new SqlDataAdapter();
DataTable table1 = new DataTable();
SqlCommand command1 = new SqlCommand();
Clear();
conn = new SqlConnection(ConfigurationManager.
ConnectionStrings["dbConnection1"].ConnectionString);
command1.Connection = conn;
command1.CommandType = CommandType.StoredProcedure;
command1.CommandText = "LargestCustID";
command1.Connection.Open();
int id = (int)command1.ExecuteScalar() + 1;
txtCustID.Text = id.ToString();
command1.Dispose();
conn.Close();
}
protected void btnAdd_Click(object sender, EventArgs e)
{
conn = new SqlConnection(ConfigurationManager.
ConnectionStrings["dbConnection1"].ConnectionString);
SqlCommand command = new SqlCommand();
command.Connection = conn;
command.CommandType = CommandType.StoredProcedure;
command.CommandText = "AddCustomer";
command.Connection.Open();
command.Parameters.AddWithValue("@CustID",
int.Parse(txtCustID.Text));
command.Parameters.AddWithValue("@Firstname", txtFirstname.Text);
command.Parameters.AddWithValue("@Surname", txtSurname.Text);
command.Parameters.AddWithValue("@Gender", rbtGender.SelectedValue);
command.Parameters.AddWithValue("@Age", int.Parse(txtAge.Text));
command.Parameters.AddWithValue("@Address1", txtAddress1.Text);
command.Parameters.AddWithValue("@Address2", txtAddress2.Text);
command.Parameters.AddWithValue("@City", txtCity.Text);
command.Parameters.AddWithValue("@Phone", txtPhone.Text);
command.Parameters.AddWithValue("@Mobile", txtMobile.Text);
command.Parameters.AddWithValue("@Email", txtEmail.Text);
adapter.InsertCommand = command;
adapter.InsertCommand.ExecuteNonQuery();
lblMessage.Text = "The new record has been added to the database!";
command.Connection.Close();
Clear();
}
protected void btnRetrieve_Click(object sender, EventArgs e)
{
conn = new SqlConnection(ConfigurationManager.
ConnectionStrings["dbConnection1"].ConnectionString);
SqlCommand command = new SqlCommand();
command.Connection = conn;
command.CommandType = CommandType.StoredProcedure;
command.CommandText = "GetCustID";
command.Connection.Open();
SqlParameter param = new SqlParameter();
param.ParameterName = "@CustID";
param.SqlDbType = SqlDbType.Int;
param.Direction = ParameterDirection.Input;
param.Value = int.Parse(txtCustID.Text);
command.Parameters.Add(param);
adapter.SelectCommand = command;
adapter.Fill(table);
int id = table.Rows.Count;
if (id == 0)
{
lblMessage.Text = "Customer ID does not exists!";
}
else
{
lblMessage.Text = "";
txtFirstname.Text = table.Rows[0].Field<string>("Firstname");
txtFirstname.DataBind();
txtSurname.Text = table.Rows[0].Field<string>("Surname");
txtSurname.DataBind();
txtAge.Text = table.Rows[0].Field<int>("Age").ToString();
txtAge.DataBind();
txtAddress1.Text = table.Rows[0].Field<string>("Address1");
txtAddress1.DataBind();
txtAddress2.Text = table.Rows[0].Field<string>("Address2");
txtAddress2.DataBind();
txtCity.Text = table.Rows[0].Field<string>("City");
txtCity.DataBind();
txtPhone.Text = table.Rows[0].Field<string>("Phone");
txtPhone.DataBind();
txtMobile.Text = table.Rows[0].Field<string>("Mobile");
txtMobile.DataBind();
txtEmail.Text = table.Rows[0].Field<string>("Email");
txtEmail.DataBind();
}
command.Connection.Close();
}
protected void btnUpdate_Click(object sender, EventArgs e)
{
conn = new SqlConnection(ConfigurationManager.
ConnectionStrings["dbConnection1"].ConnectionString);
SqlCommand command = new SqlCommand();
command.Connection = conn;
command.CommandType = CommandType.StoredProcedure;
command.CommandText = "UpdateCustomer";
command.Connection.Open();
command.Parameters.AddWithValue("@CustID",
int.Parse(txtCustID.Text));
command.Parameters.AddWithValue("@Firstname", txtFirstname.Text);
command.Parameters.AddWithValue("@Surname", txtSurname.Text);
command.Parameters.AddWithValue("@Gender", rbtGender.SelectedValue);
command.Parameters.AddWithValue("@Age", int.Parse(txtAge.Text));
command.Parameters.AddWithValue("@Address1", txtAddress1.Text);
command.Parameters.AddWithValue("@Address2", txtAddress2.Text);
command.Parameters.AddWithValue("@City", txtCity.Text);
command.Parameters.AddWithValue("@Phone", txtPhone.Text);
command.Parameters.AddWithValue("@Mobile", txtMobile.Text);
command.Parameters.AddWithValue("@Email", txtEmail.Text);
lblMessage.Text = "The record has been updated!";
command.Connection.Close();
Clear();
}
protected void btnDelete_Click(object sender, EventArgs e)
{
try
{
conn = new SqlConnection(ConfigurationManager.
ConnectionStrings["dbConnection1"].ConnectionString);
SqlCommand command = new SqlCommand();
command.Connection = conn;
command.CommandType = CommandType.StoredProcedure;
command.CommandText = "DeleteCustomer";
command.Connection.Open();
SqlParameter param = new SqlParameter();
param.ParameterName = "@CustID";
param.SqlDbType = SqlDbType.Int;
param.Direction = ParameterDirection.Input;
param.Value = int.Parse(txtCustID.Text);
command.Parameters.Add(param);
adapter.DeleteCommand = command;
adapter.DeleteCommand.ExecuteNonQuery();
int id = (int)param.Value;
command.Connection.Close();
}
catch (Exception ex)
{
lblMessage.Text += "Please enter Customer ID!";
}
try
{
lblMessage.Text = "";
SqlParameter param = new SqlParameter();
param.ParameterName = "@CustID";
param.SqlDbType = SqlDbType.Int;
param.Direction = ParameterDirection.Input;
param.Value = int.Parse(txtCustID.Text);
command.Parameters.Add(param);
adapter.DeleteCommand = command;
adapter.DeleteCommand.ExecuteNonQuery();
int id = table.Rows.Count;
id = (int)param.Value;
lblMessage.Text += "Customer record has been deleted";
command.Connection.Close();
}
catch (Exception ex)
{
lblMessage.Text = "Customer ID doesnot exists!";
}
Clear();
}
public string CustID { get; set; }
}
}
听起来您正试图通过使用异常来控制应用程序的流。反对这种方法的原因有很多：
1） 代码很难理解和调试。
2） 正在中引发异常。网络是昂贵的。
3） 如果应用程序的异常控制流，您如何将它们与真正的异常（当某些事情不能按预期工作时抛出）区分开来？
另一方面，如果您想在问题中列出的任何场景发生时抛出异常，则可以使用标准。净Exception类：
if (string.IsNullOrWhiteSpace(txtCustID.Text))
{
throw new Exception("Id not provided.");
}
或者，您可以创建一个自定义异常来提供一些更具体的信息：
public class IdNotProvidedException : Exception
{
public string MyCommandName { get; set; }
public IdNotProvidedException(string msg)
: base(msg)
{
}
public IdNotProvidedException(string msg, string myCommandName)
: base(msg)
{
this.MyCommandName = myCommandName;
}
}
然后初始化并抛出自定义异常。
最后，虽然问题中没有提到，但代码中已经有一些地方值得封装在try...catch块中。基本上，与服务器连接的任何地方都可能导致意外情况（例如，服务器可能不可用）。