Stored Procedure To Insert Record

I have an SP to add a record to the database but i get the error shown below. Any help appreciated.





Stored Procedure:





CREATE PROCEDURE addUser


@username char(15),


@password char(12)





AS


INSERT INTO users(username, password) VALUES (@username, @password)





GO








Code calling SP:





Dim myConnection As New System.Data.SqlClient.SqlConnection(ConnectionString)





Dim cmd As New SqlCommand("addUser", myConnection)


MyDataAdapter = New SqlDataAdapter()


'MyDataAdapter = New SqlDataAdapter("addUser", myConnection)





With cmd 'MyDataAdapter


.CommandType = CommandType.StoredProcedure


.Parameters.Add("@username", SqlDbType.Char).Value = username


.Parameters.Add("@password", SqlDbType.Char).Value = password


End With





Try


myConnection.Open()


cmd.ExecuteNonQuery()


Catch ex As SqlException


Finally


myConnection.Close()


End Try








I get an error message on the line: cmd.ExecuteNonQuery()





System.FormatException: Input string was not in a correct format.