I have a table in a database that populates a drop down list and I also have a list item that is appended with the value = 0.  Is there any way to set this value to be Null because having the value = 0 is giving me a FKey constraint error.  The idea of my web page is:  I have 6 drop down lists each with its own list of parts.  I want to the user to be able to mix and match parts according to selection and click the button event to insert the parameter values into the database.  But the trick is to allow the drop down list to insert Null values because the user may only want to match 2 parts from 2 drop down lists and the other 4 drop down list need to insert Null values. can someone give me any ideas on how to fix this?

here is the code for one dropdown list. I figured if I can get one to insert a null value,  I can get all of them to work. 

can you give me an example how to convert it?

if (s.Trim() == string.Empty) return null;

try

/// <summary>

/// Convert empty or null to default value

/// </summary>

/// <param name="s">Input value</param>

/// <param name="defaultValue">default value</param>

/// <returns>return default value or input value</returns>

if (s.Trim() == string.Empty) return defaultValue;

if (s.Trim() == string.Empty) return null;

try

/// <summary>

/// Convert empty or null to default value

/// </summary>

/// <param name="s">Input value</param>

/// <param name="defaultValue">default value</param>

/// <returns>return default value or input value</returns>

if (s.Trim() == string.Empty) return defaultValue;

i really hope you wouldn't try the other method since it would be so easy just to insert a null value to the list

Fistrt off, I am using an object data source to inert my vales. SO I need to figure out a way using this method.  

'inserts new match

lblStatus.Text = "New record was added to the database."

Try the follow way, it is easy for you. 

Dim componentTypeMatchingAdapter As New managementTableAdapters.componentTypeMatchingTableAdapter componentTypeMatchingAdapter.InsertCompTypeMatch(

ddlMount.SelectedValue==0?null:ddlMount.SelectedValue,

ddlInstruments.SelectedValue, ddlEngine.SelectedValue, ddlPaint.SelectedValue, ddlGenerator.SelectedValue, ddlCool.SelectedValue, ddlElectrical.SelectedValue, ddlSafety.SelectedValue) GridView1.DataBind() lblStatus.Text = "New record was added to the database."

the above solution is much better

thanks for the replies. now I am getting a specified cast is not valid error??

   Protected Sub btnAddComp_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAddComp.Click

        'inserts new match
        Dim componentTypeMatchingAdapter As New managementTableAdapters.componentTypeMatchingTableAdapter
        componentTypeMatchingAdapter.InsertCompTypeMatch(IIf(ddlMount.SelectedValue = 0, Nothing, ddlMount.SelectedValue), ddlInstruments.SelectedValue, IIf(ddlEngine.SelectedValue = 0, Nothing, ddlEngine.SelectedValue), ddlPaint.SelectedValue, ddlGenerator.SelectedValue, ddlCool.SelectedValue, ddlElectrical.SelectedValue, ddlSafety.SelectedValue)
        GridView1.DataBind()
        lblStatus.Text = "New record was added to the database."

        'goes to add a match view
        MultiView1.ActiveViewIndex = "1"
    End Sub

I am using SQL server 2005 and the allow Nulls property is set to 'yes' on all my columns. Is there something else I need to check?

I mean for the parameter in function

 In C# need to use

private void Method (int? id)

{

}

is your vb.net has the same sentence?

I am not sure if the parameter excepts System.Nullable class.  I am using a dataset with several Table adapters. This one is unsing the componentTypeTableadapter with an Insert stored procedure as one of the methods. All I do is call this procedure like the following and fill in the parameters.

    Protected Sub btnAddComp_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAddComp.Click

        'inserts new match
        Dim componentTypeMatchingAdapter As New managementTableAdapters.componentTypeMatchingTableAdapter
        componentTypeMatchingAdapter.InsertCompTypeMatch(ddlMount.SelectedValue, ddlInstruments.SelectedValue, ddlEngine.SelectedValue, 
        ddlPaint.SelectedValue, ddlGenerator.SelectedValue, 
        ddlCool.SelectedValue, ddlElectrical.SelectedValue,
        ddlSafety.SelectedValue)

        GridView1.DataBind()
        lblStatus.Text = "A new record was added to the database."

        'goes to add a match view
        MultiView1.ActiveViewIndex = "1"
    End Sub