C# 如何在违反唯一密钥时获取警报
如果数据库检测到唯一密钥冲突,则此行C# 如何在违反唯一密钥时获取警报,c#,alert,unique-key,C#,Alert,Unique Key,如果数据库检测到唯一密钥冲突,则此行 protected void Button1_Click(object sender, EventArgs e) { SqlConnection myConnection = new SqlConnection("server=VIVID-PC;Integrated Security = True;Database=SchoolDb"); SqlCommand myCommand = new SqlCommand("
protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection myConnection = new SqlConnection("server=VIVID-PC;Integrated Security = True;Database=SchoolDb");
SqlCommand myCommand = new SqlCommand("Command String", myConnection);
myConnection.Open();
string firstText = TextBox1.Text;
string SecondText = TextBox2.Text;
string thirdText = TextBox3.Text;
string fourthText = TextBox4.Text;
myCommand = new SqlCommand("INSERT INTO SchoolDb_Student(StudentName,RollNo,Session,MobileNo)values('" + firstText + "','" + SecondText + "' , '" + thirdText + "','" + fourthText + "')", myConnection);
myCommand.ExecuteNonQuery();
myConnection.Close();
Response.Redirect("/view.aspx");
}
将引发异常。您可以捕获该异常并继续使用自己的代码:
myCommand.ExecuteNonQuery();
请注意,您的代码容易受到SQL注入攻击。您应该使用命令参数,而不是手动构建SQL。此外,您应该使用使用块()如果无法将行插入数据库,则会引发异常。在你的情况下,这很可能是一个错误。抓住它。使用您的(阅读备注部分)来检测插入失败。您可以使用异常或受影响零件的行数
试试这个:
try
{
myCommand.ExecuteNonQuery();
}
catch(Exception e)
{
// right here, "something" went wrong. Examine e to check what it was.
}
试试看
{
…剩下的代码
...
int rowsAffected=myCommand.ExecuteNonQuery();//最有可能的情况是,在唯一密钥冲突的情况下,它将引发异常。否则,仍然没有行受到影响
如果(rowsAffected如注释中所示,请使用命令参数
try
{
... your rest of the code
...
int rowsAffected = myCommand.ExecuteNonQuery(); // Most probaboly it will throw exception in case of Unique key violation. If not, still no rows have been affected
if(rowsAffected<1)
{
//your Alert for no records inserted
}
else
{
//your alert for successful insertion
}
}
catch(SqlException ex)
{
//check the exception and display alert
}
finally
{
//release connection and dispose command object
}
您还可以在catch块中循环不同的sql错误
确保您处理了连接和命令()
不要创建虚拟命令对象
以下是完整的代码:
try
{
//Your other code
_myCommand.ExecuteNonQuery();
myConnection.Close();
Response.Redirect("/view.aspx");
}
catch(SqlException sqlExc)
{
// Your popup or msg.
}
进一步考虑-改进代码中的命名-TextBox1、TextBox2等对读者来说没有任何意义。给他们适当的名称,如StudentNameTextBox、RollNoTextBox等。另外,最好的做法是拆分数据访问和UI逻辑。检测到。使用命令参数,我找不到你。具体帮助我,我是初学者。你可以单击linkthnks为suggestionanytime好友,快乐编码
using(var connection = new SqlConnection(connectionString))
using(var command = connection.CreateCommand())
{
command.CommandText =
@"INSERT INTO SchoolDb_Student(StudentName,RollNo,Session,MobileNo)
VALUES (@studentName, @rollNo, @session, @mobileNo)";
command.Parameters.AddWithValue("studentName", TextBox1.Text);
command.Parameters.AddWithValue("rollNo", TextBox2.Text);
command.Parameters.AddWithValue("session", TextBox3.Text);
command.Parameters.AddWithValue("mobileNo", TextBox4.Text);
connection.Open();
try
{
command.ExecuteNonQuery();
}
catch(SqlException e)
{
if (e.Message.Contains("Violation of UNIQUE KEY constraint"))
// you got unique key violation
}
}