Very Strange SqlClient error with SmallDatetime parameter in SQL Server 2014 stored proc - vb.net

Question

I've been stumped with the following error for the past hour:
"Procedure or function 'write_call' expects parameter '#Date', which was not supplied."
The #date parameter is a smalldatetime. I am trying to pass the value #1/27/2009 04:32:00 PM#
I am using SQLExpress 2014.
The same stored proc has been in production on SQLExpress 2008
T-SQL Stored Proc:
ALTER proc [dbo].[write_call]
(
#Date smalldatetime, #Duration smallint, #Ring tinyint, #Extension smallint = null, #Number varchar(20) = null, #LineID smallint,
#AccountID smallint = null, #AccountName varchar(30) = null, #UnitID smallint = null, #UnitName varchar(30) = null, #AreaName varchar(100) = null, #CallType char(1) = null,
#CallCode varchar(6) = null, #Rate numeric(5,2) = 0.0, #Cost numeric(12,2) = 0.0, #TAC varchar(10) = null
)
as
declare #id int=0, #old_acctid int=0 --, #old_rate numeric(5,2)=0.0, #old_cost numeric(12,2)=0.0
select #id=o.ID,#old_acctid=o.AccountID from OutboundCalls o where o.Date=#Date and o.Duration=#Duration and o.Number=#Number
if #id=0
begin
insert into _OutboundCalls (Date, Duration, Ring, Extension, Number, LineID, AccountID, AccountName, UnitID, UnitName, AreaName, CallType,CallCode, Rate, Cost, TAC,redirected,contactid,CompanyID,CompanyName)
values (#Date, #Duration, #Ring, #Extension, #Number, #LineID, #AccountID, #AccountName, #UnitID, #UnitName, #AreaName, #CallType, #CallCode, #Rate, #Cost, #TAC,1,0,1,'PricewaterhouseCoopers')
end
else if #id>0 and #old_acctid<>#AccountID
update OutboundCalls set AccountID=#AccountID, UnitID=#UnitID,AccountName=#AccountName,UnitName=#UnitName
where OutboundCalls.ID=#id
VB.NET 2015:
Private Sub write_call(c As CallInfo)
Using cnn = New SqlClient.SqlConnection(connString)
Using cmd = New SqlClient.SqlCommand("write_call", cnn)
cmd.Parameters.AddWithValue("#Date", c.dt)
cmd.Parameters.AddWithValue("#Duration", c.secDurn)
cmd.Parameters.AddWithValue("#Ring", 0)
cmd.Parameters.AddWithValue("#Extension", c.src)
cmd.Parameters.AddWithValue("#Number", c.dst)
cmd.Parameters.AddWithValue("#LineID", c.lineId)
cmd.Parameters.AddWithValue("#AccountID", c.account_id)
cmd.Parameters.AddWithValue("#AccountName", c.account_name)
cmd.Parameters.AddWithValue("#UnitID", c.unit_id)
cmd.Parameters.AddWithValue("#UnitName", c.unit_name)
cmd.Parameters.AddWithValue("#AreaName", c.area?.Name)
cmd.Parameters.AddWithValue("#CallType", c.dst_type)
cmd.Parameters.AddWithValue("#CallCode", c.callcode)
cmd.Parameters.AddWithValue("#Rate", c.rate?.rate)
cmd.Parameters.AddWithValue("#Cost", c.Cost)
cmd.Parameters.AddWithValue("#TAC", c._oC)
cnn.Open()
Try
cmd.ExecuteNonQuery()
Catch ex As Exception
Stop
End Try
End Using
End Using
End Sub

Answer 1

It seems that your code misses to set the CommandType property. This property defaults to CommandType.Text and it is appropriate when you pass a sql string as the CommandText.
If you pass the name of a stored procedure you need to set
cmd.CommandType = CommandType.StoredProcedure
without this setting the behavior of the SqlCommand is unpredictable.