Question

我是新手。

我正在尝试检查重复的数据库条目。我的问题是：

如果条目成功，我希望显示成功提示。
如果存在重复，则显示重复的通知。

我的问题是：重复警报会多次显示，但是，如果不存在重复项，则永远不会创建该条目。

这是我的代码：

/// <summary>
/// The following procedure creates the user account in the database The procedure first attempts to
/// perform a check for duplicates before submitting the registration info
/// </summary>
protected void BTN_CreateACNT_Click(object sender, EventArgs e)
{
    string InsertQuery = "";
    string ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["Reimburse"].ConnectionString;
    InsertQuery = "Insert into TBL_Logins (FirstName, LastName, EmailAddress, Password) VALUES(@FirstName, @LastName, @EmailAddress, @Password)";

    String FirstNameSTR = FN.Text.Trim();
    String LastNameSTR = LN.Text.Trim();
    String EMailAddressSTR = EmailAddress.Text.Trim();
    byte[] PassByte = StrToByteArray(PWD.Text.Trim());

    // CheckUser(EMailAddressSTR);
    while (CheckUser(EMailAddressSTR) == false)
    {
        SqlConnection CN = new SqlConnection(ConnectionString);

        SqlCommand CMD = new SqlCommand(InsertQuery, CN);
        CMD.CommandType = CommandType.Text;
        CMD.Parameters.AddWithValue("@Firstname", FirstNameSTR);
        CMD.Parameters.AddWithValue("@LastName", LastNameSTR);
        CMD.Parameters.AddWithValue("@EmailAddress", EMailAddressSTR);
        CMD.Parameters.AddWithValue("@Password", PassByte);

        CN.Open();
        CMD.ExecuteNonQuery();
        Response.Write("<script language='javascript'>alert('Account created successfully.');</script>");
        CN.Close();
    }
}

public bool CheckUser(String UserString)
{
    String UserSelect = "Select * from TBL_Logins where EmailAddress = @EmailAddress";
    int MailCount = 0;
    string ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["Reimburse"].ConnectionString;
    SqlConnection CN = new SqlConnection(ConnectionString);
    UserString = EmailAddress.Text.Trim();

    SqlCommand CMD = new SqlCommand(UserSelect, CN);
    CMD.Parameters.AddWithValue("@EmailAddress", UserString);
    CN.Open();

    SqlDataReader dr = CMD.ExecuteReader();

    while (dr.Read())
    {
        if (UserString == dr["EmailAddress"].ToString())
        {
            Response.Write("<script language='javascript'>alert('This EMail address is already taken. Please try again.');</script>");
            // return true;
        }
    }

    CN.Close();
    return true;
}

protected void BTN_CreateACNT_Click(object sender, EventArgs e)
{
    string InsertQuery = "";
    string ConnectionString =                 System.Configuration.ConfigurationManager.ConnectionStrings["Reimburse"].ConnectionString;
    InsertQuery = "Insert into TBL_Logins (FirstName, LastName, EmailAddress, Password) VALUES(@FirstName, @LastName, @EmailAddress, @Password)";

    String FirstNameSTR = FN.Text.Trim();
    String LastNameSTR = LN.Text.Trim();
    String EMailAddressSTR = EmailAddress.Text.Trim();
    byte[] PassByte = StrToByteArray(PWD.Text.Trim());

    //  CheckUser(EMailAddressSTR);
    while(CheckUser(EMailAddressSTR) == false)
    {
            SqlConnection CN = new SqlConnection(ConnectionString);

            SqlCommand CMD = new SqlCommand(InsertQuery, CN);                    
            CMD.CommandType = CommandType.Text;
            CMD.Parameters.AddWithValue("@Firstname", FirstNameSTR);
            CMD.Parameters.AddWithValue("@LastName", LastNameSTR);
            CMD.Parameters.AddWithValue("@EmailAddress", EMailAddressSTR);
            CMD.Parameters.AddWithValue("@Password", PassByte);

            CN.Open();
            CMD.ExecuteNonQuery();
            Response.Write("<script language='javascript'>alert('Account created successfully.');</script>");
            CN.Close();
        }
    }

    public bool CheckUser(String UserString)
    {
         String UserSelect = "Select * from TBL_Logins where EmailAddress = @EmailAddress";
        int MailCount = 0;
        string ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["Reimburse"].ConnectionString;
        SqlConnection CN = new SqlConnection(ConnectionString);
        UserString = EmailAddress.Text.Trim();
        SqlCommand CMD = new SqlCommand(UserSelect,CN);
        CMD.Parameters.AddWithValue("@EmailAddress", UserString);
        CN.Open();
        SqlDataReader dr = CMD.ExecuteReader();

        while (dr.Read())
        {
                if (UserString == dr["EmailAddress"].ToString())
                {
                    Response.Write("<script language='javascript'>alert('This EMail address is already taken. Please try again.');</script>");
                    //                  return true;
                }           
        }

        CN.Close();
        return true;
    }

Answer 1

看起来CheckUser方法总是返回true，这就是插入不起作用的原因，默认情况下更新方法返回false：

while (dr.Read())
    {
            if (UserString == dr["EmailAddress"].ToString())
            {
                Response.Write("<script language='javascript'>alert('This EMail address is already taken. Please try again.');</script>");
                return true; // return true if user exists
            }           
    }

 CN.Close();
 return false; // return false if the user does not exist

还建议使用使用块来处理数据库连接，而不是手动调用Close（）方法。

Web表单：检查重复的数据库条目

1 个答案: