Avoid inserting duplicate records in c# [duplicate]

This question already exists: Closed 11 years ago.

How to avoid inserting duplicate records in c#

For exampl开发者_JAVA技巧e:

Table name: record1 in that userName is primary key

1. insert record1.(userName=101, password=raj, confirmPassword=raj)
2. insert record2.(userName=102, password=kumar, confirmPassword=kumar)
3. insert record3.(userName=101, password=jose, confirmPassword=jose)

When the ok button is clicked it shows a message like

MessageBox.Show("User name already inserted. Please change username");

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Create an index on the table on the userName column and make it Unique. This will throw an exception when a duplicate record is added.

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Are you familiar with using a database system? Maybe I'm misunderstanding you, but all you would do is run a query to see if the user exists or check on the SQL error returned if you have a constraint on the username.

If that is indeed what you were looking for, I think you should learn to use Google more often and learn SQL before diving into writing a system that requires it. :)

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You could catch the primary key violation and handle it with your error message.

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• Validate in your usertable (via a query) that the username does not exist yet
• If not, insert, else show the messagebox