Question

我在c＃中执行update语句遇到了一些问题。好吧，如果我在查询字符串中写一些特定的值，如

string querystr = "UPDATE Users SET User_FirstName='My Firstname', User_LastName='My Lastname' WHERE User_Username='username'";

但是当我使用parameter.Add在查询字符串中写入时，它不起作用。所以我遇到了一些麻烦，就是如何在我的查询字符串中使用参数。

到目前为止，这是我的剧本

SqlConnection connection = new SqlConnection("Data Source=localhost;Initial Catalog=Break; Integrated Security=True");
SqlCommand command = new SqlCommand("SELECT * FROM Users", connection);
command.Connection.Open();

string querystr = "UPDATE Users SET User_FirstName = @FirstName, User_LastName= @LastName WHERE User_Username = @Username";
SqlCommand query = new SqlCommand(querystr, connection);

string User_Username = Session["Username"].ToString();
string User_FirstName = FirstNameEdit.Text;
string User_LastName = LastNameEdit.Text;

query.Parameters.Add("@Username", User_Username);
query.Parameters.Add("@FirstName", User_FirstName);
query.Parameters.Add("@LastName", User_LastName);

query.ExecuteNonQuery();

Session.Add("FirstName", User_FirstName);
Session.Add("LastName", User_LastName);

StatusMessage.Text = "Updated!";

command.Connection.Close();

Answer 1

您正在使用SqlParameter添加Add。请改用AddWithValue：

query.Parameters.AddwithValue("@Username", User_Username);

Answer 2

首先尝试按照您在字符串中定义的顺序定义参数。在过去，我遇到了问题，但我不得不说我此时使用过ADO Connection。但这可能是一次尝试。也许参数不会在内部被名称引用。

（但我希望这不是问题。希望这已经修复了）

像这样：

SqlConnection connection = new SqlConnection("Data Source=localhost;Initial Catalog=Break; Integrated Security=True");
SqlCommand command = new SqlCommand("SELECT * FROM Users", connection);
command.Connection.Open();

string querystr = "UPDATE Users SET User_FirstName = @FirstName, User_LastName= @LastName WHERE User_Username = @Username";
SqlCommand query = new SqlCommand(querystr, connection);

string User_Username = Session["Username"].ToString();
string User_FirstName = FirstNameEdit.Text;
string User_LastName = LastNameEdit.Text;

// changed the order of adding values here
query.Parameters.Add("@FirstName", User_FirstName);
query.Parameters.Add("@LastName", User_LastName);
query.Parameters.Add("@Username", User_Username);

query.ExecuteNonQuery();

Session.Add("FirstName", User_FirstName);
Session.Add("LastName", User_LastName);

StatusMessage.Text = "Updated!";

command.Connection.Close();

Answer 3

SqlCommand query = new SqlCommand(querystr, connection);
query.CommandType = CommandType.Text //try to add this line.

并尝试为第二个sqlcommand打开一个新的sqlconnection。

Answer 4

尝试隔离更新查询并添加SqlParameters的新实例。还要检查User_Username变量是否获得数据库中存在的值。

string User_Username = Session["Username"].ToString();
string User_FirstName = FirstNameEdit.Text;
string User_LastName = LastNameEdit.Text;

string cnnStr = "Data Source=localhost;Initial Catalog=Break; Integrated Security=True";

using (SqlConnection connection = new SqlConnection(cnnStr))
{
   //Commented as not using
   //SqlCommand command = new SqlCommand("SELECT * FROM Users", connection);
   //command.Connection.Open();

   string querystr = "UPDATE Users SET User_FirstName = @FirstName, User_LastName= @LastName " +
                     "WHERE  User_Username = @Username";
   SqlCommand query = new SqlCommand(querystr, connection);

   //Add a new SqlParameter()...
   query.Parameters.Add(new SqlParameter("@Username", SqlDbType.NVarChar)).Value = User_Username;
   query.Parameters.Add(new SqlParameter("@Firstname", SqlDbType.NVarChar)).Value = User_FirstName;
   query.Parameters.Add(new SqlParameter("@LastName", SqlDbType.NVarChar)).Value = User_LastName;

   connection.Open();
   query.ExecuteNonQuery();
}

//Rest of the code
Session.Add("FirstName", User_FirstName);
Session.Add("LastName", User_LastName);
StatusMessage.Text = "Updated!";

C＃参数在查询字符串中不起作用

4 个答案: