fomat exception, datagridview, sqlite

我收到此错误：

Error: Format Exception: Input string was not in a correct format.

在

foreach (DataRow row in dtChanges.Rows)
            {
                using (SQLiteConnection conn = new SQLiteConnection(connString))
                {
                    conn.Open();
                    SQLiteCommand upCmd = new SQLiteCommand(@"update.......",conn);
           upCmd.Parameters.AddWithValue("@Flux",float.Parse(row["Flux"].ToString()));

此行["Flux"] 来自数据网格视图。它可以是一个 " 字符串。我想这就是导致问题的原因。通量是数据库中的数字。我是sqlite DB。我理解这个错误，即"不能转换为小数。但是解决这个问题的最佳方法是什么？

Stack Trace: 
       at System.Number.ParseSingle(String value, NumberStyles options, NumberFormatInfo numfmt)
       at System.Single.Parse(String s)
       at RVEST.frmVesselData.SaveData(DataGridView dgv) in C:'D_Drive_Stuff'RVESTV2'RVEST'frmVesselData.cs:line 249
       at RVEST.frmVesselData.btnSave_Click(Object sender, EventArgs e) in C:'D_Drive_Stuff'RVESTV2'RVEST'frmVesselData.cs:line 190
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at RVEST.Program.Main() in C:'RVEST'Program.cs:line 26
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()

谢谢你太阳

float result;
result = row["flux"] != null && float.TryParse(row["flux"].ToString(), out result) ? result :0;
upCmd.Parameters.AddWithValue("@Flux", result);

float result;
    var res= row["flux"] != null && float.TryParse(row["flux"].ToString(), out result) ? (float?)result :null;
upCmd.Parameters.AddWithValue("@Flux", res);