To modify existing records, use UPDATE statements.

Update Syntax

The UPDATE statement takes as input a comma-separated list of columns and new column values as name-value pairs in the SET clause, as shown in the following example:

UPDATE <table_name> SET <select_statement> | {<column_reference> = <expression> [ , ... ]} WHERE { Id = <expression>  } [ { AND | OR } ... ] 

<expression> ::=
  | @ <parameter> 
  | ?
  | <literal>

You can use the ExecuteNonQuery method to execute data manipulation commands and retrieve the rows affected, as shown in the following example:

C#

String connectionString = "Port=993;Server=outlook.office365.com;Password=password;User=user;Protocol=IMAP;SMTP Port=587;SMTP Server=smtp.office365.com;";
using (EmailConnection connection = new EmailConnection(connectionString)) {
  int rowsAffected;
  EmailCommand cmd = new EmailCommand("UPDATE [INBOX] SET Subject='Spam' WHERE Id = @myId", connection);
  cmd.Parameters.Add(new EmailParameter("myId","1"));
  rowsAffected = cmd.ExecuteNonQuery();
}

VB.NET

Dim connectionString As [String] = "Port=993;Server=outlook.office365.com;Password=password;User=user;Protocol=IMAP;SMTP Port=587;SMTP Server=smtp.office365.com;"
Using connection As New EmailConnection(connectionString)
  Dim rowsAffected As Integer
  Dim cmd As New EmailCommand("UPDATE [INBOX] SET Subject='Spam' WHERE Id = @myId", connection)
  cmd.Parameters.Add(New EmailParameter("myId", "1"))
  rowsAffected = cmd.ExecuteNonQuery()
End Using