Update Stored Procedure Not Updating

Hello,
I'm working on a grant management database for a project in my databases class and I'm having some issues updating grants into the database.
Here is my situation:
How this page works is, it gets a query string from a search_grant.aspx page.  In this query string, it gets the grant ID of the grant the user wants to edit.  If the grant id is a valid grant, it then, upon page_load in C#:
1.) Creates an Sql connection set to a viewGrant stored procedure,
2.) Adds in all the necessary parameters as output variables
3.) Sets private members declared inside of the partial class to those values it gets from the stored procedure
4.) Sets textbox controls on the page to those values
5.) Displays the page with all the populated data from the stored procedure

That part works fine.  I was having an issue where clicking the update button would not grab the new values that the user input into the textboxes.  I later realized that the Page_Load code was being re-executed BEFORE the button was being clicked (kind of dumb but...whatever).  To fix it, I placed all of the code to do the above statements inside of a:
if (!Page.IsPostBack)
{
// Do code here
}
That works fine.  The problem, however, is that it's STILL not updating.  The stored procedure works just fine inside of the management studio, but not in the ASP Page.  The code is similar to that of my new_grant.aspx page, which creates a grant into the database.  Why that works and this doesn't, I don't know.  Even when I hard code the values into the parameters in C#, it's not updating the data!  There are no errors that are being returned, so this has really boggled my mind.
Any help is greatly appreciated!

Here is some sample code of what I'm doing:protected void Update_button_Click(object sender, EventArgs e)
{
// Create SQL connection to update Grant
string ConnectionString = "connection string which works fine";
SqlConnection sqlConnection2 = new SqlConnection();

try
{
sqlConnection2.ConnectionString = ConnectionString;
sqlConnection2.Open();
}
catch (Exception Ex)
{
if (sqlConnection2 != null) { sqlConnection2.Dispose(); }

SQLErrorLabel.Text = Ex.Message;
SQLErrorLabel.Visible = true;
return;
}

// ------------------ Update values into database -------------------


// Create the statement to use on the database
SqlCommand editGrant = new SqlCommand("editGrant", sqlConnection2);
editGrant.CommandType = CommandType.StoredProcedure;
editGrant.Connection = sqlConnection2;


// Set our values for each variable
GrantName = GrantName_input.Text;
ProjectDescription = ProjDesBox.Text;
ReportingYear = Int32.Parse(ReportYearBox.SelectedItem.ToString());
ActivityStarted = Activity_Date.Text;
DateSubmitted = Date_Submitted.Text;
Audit = chkAudit.Checked;
TypeID = Type_ID_input.SelectedValue;
FunderID = Funder_List.SelectedValue;
StatusID = Status_ID_input.SelectedValue;
AcademicDepartmentID = AcademicID_List.SelectedValue;
PIID = PI_List.SelectedValue;
ContractNumber = txtContractNum.Text;
ESUAccountNumber = txtESUAccountNum.Text;
AmountAwarded = txtAmount.Text;
AwardDate = Award_Date.Text;
DateContractSigned = txtDateSigned.Text;
ReportingNotes = ReportingNotesbox.Text;
NotesNotes = GrantNotesbox.Text;

string ReportingTimestamp = DateTime.Now.ToString();
string ReportingWho = Membership.GetUser().ToString();
string NotesTimestamp = DateTime.Now.ToString();
string NotesWho = Membership.GetUser().ToString();

#region insertParams
// Add our parameters that SQL will be using
editGrant.Parameters.AddWithValue("@GrantID", GID);
editGrant.Parameters["@GrantID"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@GrantName", GrantName);
editGrant.Parameters["@GrantName"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ProjectDescription", ProjectDescription);
editGrant.Parameters["@ProjectDescription"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ReportingYear", ReportingYear);
editGrant.Parameters["@ReportingYear"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ActivityStarted", ActivityStarted);
editGrant.Parameters["@ActivityStarted"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@DateSubmitted", DateSubmitted);
editGrant.Parameters["@DateSubmitted"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@Audit", Audit);
editGrant.Parameters["@Audit"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@TypeID", TypeID);
editGrant.Parameters["@TypeID"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@StatusID", StatusID);
editGrant.Parameters["@StatusID"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@FunderID", FunderID);
editGrant.Parameters["@FunderID"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@AcademicDepartmentID", AcademicDepartmentID);
editGrant.Parameters["@AcademicDepartmentID"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@PIID", PIID);
editGrant.Parameters["@PIID"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ContractNumber", ContractNumber);
editGrant.Parameters["@ContractNumber"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ESUAccountNumber", ESUAccountNumber);
editGrant.Parameters["@ESUAccountNumber"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@AmountAwarded", AmountAwarded);
editGrant.Parameters["@AmountAwarded"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@AwardDate", AwardDate);
editGrant.Parameters["@AwardDate"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@DateContractSigned", DateContractSigned);
editGrant.Parameters["@DateContractSigned"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ReportingNotes", ReportingNotes);
editGrant.Parameters["@ReportingNotes"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ReportingTimestamp", ReportingTimestamp);
editGrant.Parameters["@ReportingTimestamp"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@ReportingWho", ReportingWho);
editGrant.Parameters["@ReportingWho"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@NotesNotes", NotesNotes);
editGrant.Parameters["@NotesNotes"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@NotesTimestamp", NotesTimestamp);
editGrant.Parameters["@NotesTimestamp"].Direction = ParameterDirection.Input;

editGrant.Parameters.AddWithValue("@NotesWho", NotesWho);
editGrant.Parameters["@NotesWho"].Direction = ParameterDirection.Input;
#endregion

// Execute the UPDATE statement to Grant
editGrant.ExecuteNonQuery();
sqlConnection2.Close();
sqlConnection2.Dispose();

Response.Redirect("editedGrant.aspx?id=" + GrantIDBox.Text);
}EDIT: Problem Solved! Problem was the that the GrantID wasn't being properly set.