Question about triggering an event by clicking the button !!

爆牙珍

I click the button to check if this field exists in the database, how to change the code. If there is a prompt, it can't be taken. If there is no prompt, you can use this name!
Trouble enlighten me !!

shenmue024

SqlConnection conn = null;
SqlCommand cmd = null;
DataSet ds = new DataSet ();
string strConnectionString = "Data Source = .; initial catalog = database; uid = sa; pwd = xxx";
string strSQL = "SELECT 1 from table where field = 'aa'"
try
{
conn = new SqlConnection (strConnectionString);
conn.Open ();
cmd = new SqlCommand (strSQL, conn);
if (cmd.ExecuteScalar () == null)
{
                                  //does not exist
} else
{
// Exist.
}
Ranch
Ranch
}
catch (System.Exception e)
{
this.Text1.Text = "Error" + e.Message;
}
finally
{
if (conn! = null)
conn.Dispose ();
if (cmd! = null)
cmd.Dispose ();
}

爆牙珍

Hello, what does it mean to write in catch?
Did you try it with a text box, right, showing the wrong message?

So if I have set a button, how do I write it?

alexjjj

e.Message; is to automatically track errors and put them into this.Text1.Text, OK! !!

叽里呱啦1

The catch is to report specific error information when an exception occurs. It is also important for a real programmer to write the error message.

shenmue024is written in the Click of the button, but it is obtained through the TextBox in the field function, you can add the button event above. Not quite understand what you mean? ? ? Could it be that the field value you want to query is the value of the button? ? ? Otherwise where do you get the field values ​​from?

爆牙珍

So I just want to add a TextBox control? Capture errors in catch?
Thank you guys.

alexjjj

If it is a button, then write the above code in the check event of the button:
: This.Text1.Text = "Error" + e.Message;
To:
Response.Write ("<script language = javascript> alert ('" + "Error" + e.Message; + "'); </ script>");

It's OK. . . Try

alexjjj

The previous "" is wrong, change it yourself

爆牙珍

No, it seems wrong. The client statement above.

爆牙珍

A local variable named "e" cannot be declared in this scope because it would give "e" a different meaning, and it is already used in the "parent or current" scope to indicate something else


catch (System.Exception e) is this: