c# - 名称 '"' 在当前上下文中不存在

Question

我的代码中遇到了几个错误。这些错误是:

• 错误 17 当前上下文中不存在名称“CommandType”
• 错误 18 当前上下文中不存在名称“SqlDbType”
• 错误 35 当前上下文中不存在名称“txtCity”

我希望您能帮助我理解该错误并告诉我如何修复它。

protected void btnSave_Click(object sender, EventArgs e)
{
    // create connectionstring and insert statment
    string connectionString = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
    string insertSql = " INSERT INTO UserInfo (UID, FN, LN, Password, RePass, Email, Country,State, City)" +
        " values (@UsrNme, @fnbox, @lnamebox, @passtxtbx1, @passtxtbx2, @emailbox, @DrDncoundrlst, @DropDownListSwestate, @citytxtbox)";

    // create SQL Connection

    SqlConnection con = new SqlConnection(connectionString);

    // create sql command and parameters

    SqlCommand cmd = new SqlCommand();
    cmd.Connection = con;
    cmd.CommandType = CommandType.text;
    cmd.CommandText = insertSql;

    SqlParameter UID = new SqlParameter("@UsrNme", SqlDbType.nvarchar, 50);
    UID.Value = txtUID.text.tostring();
    cmd.Parameters.Add(UID);

    SqlParameter FN = new SqlParameter("@fnbox", SqlDbType.varchar,25);
    cmd.Connection = con;
    FN.Value = txtfn.text.ToString();
    cmd.Parameters.Add(FN);



    SqlParameter LN = new SqlParameter("@lnamebox", SqlDbType.varchar, 25);
    cmd.Connection = con;
    LN.Value = txtLN.text.ToString();
    cmd.Parameters.Add(LN);

    SqlParameter Password = new SqlParameter("@passtxtbx1", SqlDbType.varchar, 25);
    cmd.Connection = con;
    Password.Value = txtPassword.text.ToString();
    cmd.Parameters.Add(Password);


    SqlParameter RePass = new SqlParameter("@passtxtbx2", SqlDbType.varchar, 25);
    cmd.Connection = con;
    RePass.Value = txtRePass.text.ToString();
    cmd.Parameters.Add(RePass);


    SqlParameter Email = new SqlParameter("@emailbox", SqlDbType.varchar, 25);
    cmd.Connection = con;
    Email.Value = txtEmail.text.ToString();
    cmd.Parameters.Add(Email);

    SqlParameter Country = new SqlParameter("@DrDncoundrlst", SqlDbType.varchar, 25);
    cmd.Connection = con;
    Country.Value = txtCountry.text.ToString();
    cmd.Parameters.Add(Country);

    SqlParameter State = new SqlParameter("@DropDownListSwestate", SqlDbType.varchar, 25);
    cmd.Connection = con;
    State.Value = txtState.text.ToString();
    cmd.Parameters.Add(State);

    SqlParameter City = new SqlParameter("@citytxtbox", SqlDbType.varchar, 25);
    cmd.Connection = con;
    City.Value = txtCity.text.ToString();
    cmd.Parameters.Add(City);

    try
    {
        con.Open();
        cmd.ExecuteNonQuery();
        lblmsg.Text = "You already complete your registration process";
    }
    catch (SqlException ex)
    {
        string errorMessage = "error in registration user";
        errorMessage += ex.Message;
        throw new Exception(errorMessage);
    }

    finally
    {
        con.Close();
    }

}

Answer 1

你可能把事情过于复杂化了。尝试以下代码...

var connection = new SqlConnection(connectionString);
var cmd = new SqlCommand(insertSql, connection);

cmd.Parameters.AddWithValue("@UsrNme", txtUID.Text.ToString());
cmd.Parameters.AddWithValue("@fnbox", txtfn.Text.ToString());
cmd.Parameters.AddWithValue("@lnamebox", txtLN.Text.ToString());
cmd.Parameters.AddWithValue("@passtxtbx1", txtPassword.Text.ToString());
cmd.Parameters.AddWithValue("@passtxtbx1", txtPassword.Text.ToString());
cmd.Parameters.AddWithValue("@passtxtbx2", txtRePass.Text.ToString());
cmd.Parameters.AddWithValue("@emailbox", txtEmail.Text.ToString());
cmd.Parameters.AddWithValue("@DrDncoundrlst", txtCountry.Text.ToString());
cmd.Parameters.AddWithValue("@DropDownListSwestate", txtState.Text.ToString());
cmd.Parameters.AddWithValue("@citytxtbox", txtCity.Text.ToString());

try
{
    cmd.Connection.Open();
    cmd.ExecuteNonQuery();
    cmd.Connection.Close();

    lblmsg.Text = "You already completed your registration process";
}
catch (SqlException ex)
{
    var errorMessage = "error in registration user";

    errorMessage += ex.Message;

    throw new Exception(errorMessage);
}
finally
{
    con.Close();
}

您还想确保声明了以下 using 子句...

using System.Data;
using System.Data.SqlClient;

...并且 txtCity 是您实际调用的文本框，并且它不会通过 private 标识符对此方法隐藏，或者实际上显示在不同的表单上因为您收到的错误意味着该变量超出了该方法的范围，或者在您到达此方法之前其生命周期已到期。

这就是所有代码的作用。它不需要设置大量您不需要声明参数的元数据，而是让 SqlCommand 为您完成所有艰苦的工作，并根据数据库列、您传入的对象的类型以及确定什么类型是什么。参数的名称。如果您最终允许传递无效数据，那么任何复杂的元数据标记都无法使您避免错误。

同样，您确实想考虑将 insertSql 包装到 Sql Server 中的存储过程中...

create procedure adduserinfo @UsrNme               nvarchar (50),
                             @fnbox                varchar (25),
                             @lnamebox             varchar (25),
                             @passtxtbx1           varchar (25),
                             @passtxtbx2           varchar (25),
                             @emailbox             varchar (25),
                             @DrDncoundrlst        varchar (25),
                             @DropDownListSwestate varchar (25),
                             @citytxtbox           varchar (25)

as begin
   INSERT INTO UserInfo 
     ( UID, 
       FN, 
       LN, 
       Password, 
       RePass, 
       Email, 
       Country,
       State, 
       City )
   VALUES
     ( @UsrNme, 
       @fnbox, 
       @lnamebox, 
       @passtxtbx1, 
       @passtxtbx2, 
       @emailbox, 
       @DrDncoundrlst, 
       @DropDownListSwestate, 
       @citytxtbox )
end
go

那么您的 SqlCommand 声明将如下所示...

var command = new SqlCommand("adduserinfo", connection) 
{ 
    CommandType = CommandType.StoredProcedure; 
}

...其余的您将遵循我上面提供的其余代码。这或多或少是正确的方法。冒着听起来挑剔的风险，请考虑提供更多信息且格式一致的变量和参数名称。那些将来可能需要修改您的代码的人将会感谢您。