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 = "AuthScheme=Basic;User=myUser;Password=myPassword;Security Token=myToken;";
using (SalesforceConnection connection = new SalesforceConnection(connectionString)) {
  int rowsAffected;
  SalesforceCommand cmd = new SalesforceCommand("UPDATE Account SET Name='John' WHERE Id = @myId", connection);
  cmd.Parameters.Add(new SalesforceParameter("myId","1045625d-99ee-e011-a272-00155d01ad6b"));
  rowsAffected = cmd.ExecuteNonQuery();
}

VB.NET

Dim connectionString As [String] = "AuthScheme=Basic;User=myUser;Password=myPassword;Security Token=myToken;"
Using connection As New SalesforceConnection(connectionString)
  Dim rowsAffected As Integer
  Dim cmd As New SalesforceCommand("UPDATE Account SET Name='John' WHERE Id = @myId", connection)
  cmd.Parameters.Add(New SalesforceParameter("myId", "1045625d-99ee-e011-a272-00155d01ad6b"))
  rowsAffected = cmd.ExecuteNonQuery()
End Using