This how to change ah, please have a great god can teach

CodePudding user response:

See if GetDataReader returns null values

CodePudding user response:

Emmmm... I write the login screen, I went in with an administrator, and teacher does not appear this problem, the students have an error, I don't know how to return a responsibility? How can this reply is null

CodePudding user response:

Add a breakpoint, debugging

refer to 2 floor don't silly girl's reply:

emmmm... I write the login screen, I went in with an administrator, and teacher does not appear this problem, the students have an error, I don't know how to return a responsibility? How can this reply is null

CodePudding user response:

Print the SQL statement,
In the Dr Is null

CodePudding user response:

Learning under the framework
https://blog.csdn.net/dengfeiling/article/details/103627862

CodePudding user response:

Add a judgment, wow, if Dr Null will return to prompt the user does not exist

CodePudding user response:

To redefine the Dr

CodePudding user response:

Your id field is of type int, is your text box type string

CodePudding user response:

You select statement stitching has a problem, and and single quotes need a space in front of,

CodePudding user response:

A breakpoint, try debugging

CodePudding user response:

And adding Spaces