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 = "AccountEndpoint=myAccountEndpoint;AccountKey=myAccountKey;";
using (CosmosDBConnection connection = new CosmosDBConnection(connectionString)) {
  int rowsAffected;
  CosmosDBCommand cmd = new CosmosDBCommand("UPDATE [CData].[Entities].Customers SET CompanyName='Caterpillar' WHERE _id = @my_id", connection);
  cmd.Parameters.Add(new CosmosDBParameter("my_id","22"));
  rowsAffected = cmd.ExecuteNonQuery();
}

VB.NET

Dim connectionString As [String] = "AccountEndpoint=myAccountEndpoint;AccountKey=myAccountKey;"
Using connection As New CosmosDBConnection(connectionString)
  Dim rowsAffected As Integer
  Dim cmd As New CosmosDBCommand("UPDATE [CData].[Entities].Customers SET CompanyName='Caterpillar' WHERE _id = @my_id", connection)
  cmd.Parameters.Add(New CosmosDBParameter("my_id", "22"))
  rowsAffected = cmd.ExecuteNonQuery()
End Using