Trouble writing to SQL - sql-server

Question

I have been writing in VB.Net for a couple months now and have used SQL commands in my code many times successfully but am having trouble writing to one particular table in my database. I believe the problem lies in that i have a numeric column that i am trying to write to (I came to this conclusion because it is the only one i don't use very often) and my code keeps coming up with an exception: Additional information: SqlCommand.Prepare method requires all variable length parameters to have an explicitly set non-zero Size. with the code:
Dim cn As System.Data.SqlClient.SqlConnection
Dim command As System.Data.SqlClient.SqlCommand
Dim VL1 As System.Data.SqlClient.SqlParameter
Dim VL2 As System.Data.SqlClient.SqlParameter
Dim VL3 As System.Data.SqlClient.SqlParameter
Dim VL4 As System.Data.SqlClient.SqlParameter
Dim commandText As String
cn = New System.Data.SqlClient.SqlConnection(ConnectStr)
cn.Open()
commandText = "INSERT INTO [dbo].[HourMeterLog]" _
+ "([MachineName],[TotalHours],[HLRD],[DateTime])" _
+ "VALUES (#VL1,#VL2,#VL3,#VL4)"
command = New System.Data.SqlClient.SqlCommand(commandText, cn)
VL1 = command.Parameters.Add("#VL1", System.Data.SqlDbType.NVarChar, 25)
VL2 = command.Parameters.Add("#VL2", System.Data.SqlDbType.Float)
VL3 = command.Parameters.Add("#VL3", System.Data.SqlDbType.Int, 10)
VL4 = command.Parameters.Add("#VL4", System.Data.SqlDbType.DateTime2, 0)
command.Prepare()
VL1.Value = "MachineName"
VL2.Value = 0
VL3.Value = 735562
VL4.Value = Now()
command.ExecuteNonQuery()
cn.Close()
I know my code connects because I have at least 15 other queries that work using this format. I would prefer to not use float to write to the numeric field but i had it work the first time I launched this code (not once since then).

Answer 1

According to MSDN the Max character Length of the DateTime2 is 27. So I have set the Length of DateTime2 to 27 and its working fine.
VL4 = command.Parameters.Add("#VL4", System.Data.SqlDbType.DateTime2, 27)
And my working code is,
Dim cn As System.Data.SqlClient.SqlConnection
Dim command As System.Data.SqlClient.SqlCommand
Dim VL1 As System.Data.SqlClient.SqlParameter
Dim VL2 As System.Data.SqlClient.SqlParameter
Dim VL3 As System.Data.SqlClient.SqlParameter
Dim VL4 As System.Data.SqlClient.SqlParameter
Dim commandText As String
cn = New System.Data.SqlClient.SqlConnection(connectionString)
cn.Open()
commandText = "INSERT INTO [dbo].[HourMeterLog]" _
+ "([MachineName],[TotalHours],[HLRD],[DateTime])" _
+ "VALUES (#VL1,#VL2,#VL3,#VL4)"
command = New System.Data.SqlClient.SqlCommand(commandText, cn)
VL1 = command.Parameters.Add("#VL1", System.Data.SqlDbType.NVarChar, 25)
VL2 = command.Parameters.Add("#VL2", System.Data.SqlDbType.Float)
VL3 = command.Parameters.Add("#VL3", System.Data.SqlDbType.Int, 10)
VL4 = command.Parameters.Add("#VL4", System.Data.SqlDbType.DateTime2, 27)
command.Prepare()
VL1.Value = "MachineName"
VL2.Value = 0
VL3.Value = 735562
VL4.Value = Now()
command.ExecuteNonQuery()
cn.Close()

Answer 2

Okay so I guess I wrote the AddWithValue method wrong when i tried that. I got the command to write with:
Dim cn As System.Data.SqlClient.SqlConnection
Dim command As System.Data.SqlClient.SqlCommand
Dim VL1 As System.Data.SqlClient.SqlParameter
Dim VL2 As System.Data.SqlClient.SqlParameter
Dim VL3 As System.Data.SqlClient.SqlParameter
Dim VL4 As System.Data.SqlClient.SqlParameter
Dim commandText As String
cn = New System.Data.SqlClient.SqlConnection(ConnectStr)
cn.Open()
commandText = "INSERT INTO [dbo].[HourMeterLog]" _
+ "([MachineName],[TotalHours],[HLRD],[DateTime])" _
+ "VALUES (#VL1,#VL2,#VL3,#VL4)"
command = New System.Data.SqlClient.SqlCommand(commandText, cn)
VL1 = command.Parameters.AddWithValue("#VL1", "MachineName")
VL2 = command.Parameters.AddWithValue("#VL2", 0)
VL3 = command.Parameters.AddWithValue("#VL3", 735562)
VL4 = command.Parameters.AddWithValue("#VL4", Now())
'VL1 = command.Parameters.Add("#VL1", System.Data.SqlDbType.NVarChar, 25)
'VL2 = command.Parameters.Add("#VL2", System.Data.SqlDbType.Float)
'VL3 = command.Parameters.Add("#VL3", System.Data.SqlDbType.Int)
'VL4 = command.Parameters.Add("#VL4", System.Data.SqlDbType.DateTime2)
'command.Prepare()
'VL1.Value = "MachineName"
'VL2.Value = 0
'VL3.Value = 735562
'VL4.Value = Now()
command.ExecuteNonQuery()
cn.Close()
I would really prefer to use the format i had used before but i am happy that i at least am writing now. Thanks for the help guys. If anyone has any ideas on how to improve my original format to make it write correctly let me know. and for those who wanted a little info on the table I am writing too the field the Float was writing to is a Numeric(18,1) field. Other than that column the others can be extrapolated from the code.

Answer 3

For the error messge, without know anything about your table...
"SqlCommand.Prepare method requires all variable length parameters to have an explicitly set non-zero Size"
From MSDN (https://msdn.microsoft.com/en-us/library/40959t6x(v=vs.110).aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1)
'Declaration
Public Function Add ( _
parameterName As String, _
sqlDbType As SqlDbType, _
size As Integer _
) As SqlParameter
Maybe your problems comes from:
VL4 = command.Parameters.Add("#VL4", System.Data.SqlDbType.DateTime2, 0)
Change it to
VL4 = command.Parameters.Add("#VL4", System.Data.SqlDbType.DateTime2)

Answer 4

Here is a short example what the 'Size' parameter of SqlParameter has an influence.
Sample table is
CREATE TABLE [dbo].[DateTimeTest](
[CreatedAt] [datetime2](7) NOT NULL,
[SizeValue] [int] NOT NULL
) ON [PRIMARY]
Sample code in C# is
string connectionString = "Data Source=.;Integrated Security=SSPI;Initial Catalog=Sandbox";
using (SqlConnection connection = new(connectionString))
{
connection.Open();
string commandText = #"
INSERT INTO [dbo].[DateTimeTest]
([CreatedAt]
,[SizeValue])
VALUES
(#CreatedAt
,#SizeValue);
";
DateTime timestamp = DateTime.Now;
for (int i = 1; i < 28; i++)
{
SqlCommand command = new SqlCommand(commandText, connection);
SqlParameter createdAtParam = new SqlParameter("#CreatedAt", SqlDbType.DateTime2, i); // i = 0 will raise an exception on call to command.Prepare()
command.Parameters.Add(createdAtParam);
createdAtParam.Value = timestamp;
SqlParameter sizeValueParam = new SqlParameter("#SizeValue", SqlDbType.Int);
command.Parameters.Add(sizeValueParam);
sizeValueParam.Value = i;
command.Prepare();
command.ExecuteNonQuery();
}
}
As you can see, the value of 'Size' has no influence on the precision of the inserted DateTime value.
SqlParameter createdAtParam = new SqlParameter("#CreatedAt", SqlDbType.DateTime2, 0);
or
SqlParameter createdAtParam = new SqlParameter("#CreatedAt", SqlDbType.DateTime2);
will raise an exception on call to
command.Prepare();