Pass NULL value to SqlParameter based on condition using ternary operator in ASP.Net

dear sir ,

i want to pass null vaue but i can not pass null value please help me.

//balance quantity calculate in database use data set display in txtbalance.text database data type decimal1(8,2) string balanceQty txtbalance.text; // txtIssue.text client input and database data type decimal1(8,2) String IssueQty txtIssue.text;

// txtTransfer.text client input and database data type decimal1(8,2) String TransferQty txtTransfer.text;

//1.but i need frist time check balanceQty <IssueQty if result true then insert value IssueQty in database.and TransferQty ignore or null value insert in database. // and result false then lebel message show quantity exceeds. //1st condition code result ok. but 2nd condition not work at time.but separate time do the work.

//2.and again 2nd time txtIssue.text empty or null not input in client .client input to TransferQty . then check balanceQty <TransferQty //if result true then insert value TransferQtyin database.and IssueQty ignore or null value insert in database. // and result false then lebel message show quantity exceeds.

here code

                //1.but i need frist time check balanceQty <IssueQty if result true then insert value IssueQty in database.and TransferQty ignore or null value insert in database.
                // and result false then lebel message show quantity exceeds.
                //1st condition code result ok. but 2nd condition not work at time.but separate time do the work.
                ///1st condition code here,
 
                int IssueQty = 0;
                int TQty = 0;
                string tQty = txtTranstQty.Text;
                int.TryParse(tQty, out TQty);
 
                //if (txtIssueQty.Text != "")
                //{
                string issueQty = txtIssueQty.Text;
                string x = txtBlanceQty.Text;
                int.TryParse(issueQty, out IssueQty);
                // cmd.Parameters.AddWithValue("@Issue_Qty", IssueQty > 0 ? IssueQty : (object)DBNull.Value);
                if (decimal.Parse(x) < decimal.Parse(issueQty))
                {
                    lblmsg.Text = " ";
                    lblExceeds.Text = "Quantiy Exceeds";
                    lblExceeds.Visible = true;
                    lblExceeds.ForeColor = System.Drawing.Color.Red;
                    /*Pass value to your store procedure as variable value or nullable value*/
 
 
                }
                else
                {
                    // cmd.Parameters.AddWithValue("@Issue_Qty", txtIssueQty.Text);
                    cmd.Parameters.AddWithValue("@Issue_Qty", IssueQty > 0 ? IssueQty : (object)DBNull.Value);
                    cmd.Parameters.AddWithValue("@Transfer_Qty", TQty > 0 ? TQty : (object)DBNull.Value);
                    lblExceeds.Text = "";
                }
 
               //2.and again 2nd time txtIssue.text empty or null not input in client .client input to TransferQty . then check balanceQty <TransferQty
               //if result true then insert value TransferQtyin database.and IssueQty ignore or null value insert in database.
               // and result false then lebel message show quantity exceeds.
               //2nd condition code here,
                int TQty1 = 0;
                int IssueQty1 = 0;
                string issueQty1 = txtIssueQty.Text;
                //string x = txtBlanceQty.Text;
                int.TryParse(issueQty1, out IssueQty1);
               // if (txtTranstQty.Text != "")
               // {
                    string tQty1 = txtTranstQty.Text;
                    string x1 = txtBlanceQty.Text;
                    int.TryParse(tQty1, out TQty1);
 
                    if (decimal.Parse(x1) < decimal.Parse(tQty1))
                    {
                        lblmsg.Text = " ";
                        lblExceeds.Text = "Quantiy Exceeds";
                        lblExceeds.Visible = true;
                        lblExceeds.ForeColor = System.Drawing.Color.Red;
                        /*Pass value to your store procedure as variable value or nullable value*/
                    }
                    else
                    {
                        cmd.Parameters.AddWithValue("@Transfer_Qty", TQty1 > 0 ? TQty1 : (object)DBNull.Value);
                        lblExceeds.Text = "";
                        cmd.Parameters.AddWithValue("@Issue_Qty", IssueQty1 < 0 ? IssueQty1 : (object)DBNull.Value);
                    }