Try {
conn.Open();//open the channels, establishing connection

MessageBox. Show (" database connection ");

//search phone number
MySqlCommand comm=new MySqlCommand (" select * from yh1 where num1=158 ", conn);

MySqlDataReader reader=comm. ExecuteReader ();
MessageBox. Show (" checked ");
conn.Close();
Bool hr=reader. HasRows;
If (reader. HasRows)
{MessageBox. Show (hr. The ToString ()); }
//there is no phone number, register
The else
{MessageBox. Show (hr. The ToString ()); }

String wre=the string. Format (" insert yh1 (num1) values (' 151 ') ");
conn.Open();
//
MySqlCommand zhuce=new MySqlCommand (wre, conn);

Zhuce. ExecuteNonQuery ();
Kaile MessageBox. Show (" ");

conn.Close();


}
Catch
{MessageBox. Show (" write failure ");
}

CodePudding user response:

CodePudding user response:

CodePudding user response:

CodePudding user response:

The unusually,,, conn are you closed, reader can't directly access, read your shut again
Bool hr=reader. HasRows;
conn.Close();

CodePudding user response:

Finally close connections in the code

CodePudding user response:

It is ok to delete the first close, database connection is closed also check?

CodePudding user response:

Database connection open cost is higher, once opened, after query all shut down again,

CodePudding user response:

This really don't understand

CodePudding user response:

Novice said what all don't understand,,,,

CodePudding user response:

See don't understand still thank you

CodePudding user response:

So, I see

CodePudding user response:

Use WCF? ,,,,,,,

CodePudding user response:

First sqldatareader is read-only, and can only be read under the status of the database connection
The
MessageBox. Show (" checked ");
conn. Close (); Delete
Bool hr=reader. HasRows;

In addition, you always output "to failure", need to change to the following
String wre=the string. Format (" insert into the yh1 (num1) values (' 151 ') ");
conn.Open();

Remember to "post!

CodePudding user response:

So, I see

CodePudding user response:

Could you explain comm query principle? In addition, conn connection point can target? Look at the code, as you want to access to a nonexistent resources, but have not get the correct error message,

CodePudding user response:

You are close, and reader?