我有C＃代码；当运行到一行时，它抛出一个Ln = Wb.VBProject.VBComponents("Module1").CodeModule.ProcStartLine("ErrorProducingMacro", 0)
Wb.VBProject.VBComponents("Module1").CodeModule.InsertLines Ln + 2, "On Error Resume Next"
Run Wb.Name & "!ErrorProducingMacro"
。
这是引起异常的代码行
System.NullReferenceException这是代码中的堆栈跟踪
if (expDic != null && expression != null)
{
expDic.Add(i, expression.ToString())
}
我发现 at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at Sustainability.BusinessObject.CalculationManager.<>c__DisplayClass18_0.<HandleFormulaInner>b__0(Object args) in D:\HK\Desktop\VSTS_2\Sustainability.BusinessObject\Classes\CalculationManager.cs:line 1410
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
和expDic都不为空，但是它引发了空引用异常。
这是我的代码：
expression我怀疑这是由 int count = table.Rows.Count;
Dictionary<int, string> expDic = new Dictionary<int, string>();
List<Task> taskList = new List<Task>();
for (int f = 0; f < count; f++)
{
DataRow tempformula = table.Rows[f];
string formulaSymbol = Convert.ToString(tempformula[Common.Systems.Sustainability.Constants.IndicatorFormula.Symbol]);
var t = Task.Factory.StartNew(new Action<object>((args) => {
int i = (int)args;
_sem.Wait();
StringBuilder expression = new StringBuilder(1024);
using (DataTable dt = new DataTable())
{
// symbol in the last line of formula
if (exp.EndsWith("+")
|| exp.EndsWith("-")
|| exp.EndsWith("*")
|| exp.EndsWith("/"))
{
exp = exp.Substring(0, exp.Length - 1);
}
object result = dt.Compute(exp, "");
expression.Append(result);
}
}
{
if (!string.IsNullOrWhiteSpace(symbol)
&& expression.Length > 0)
{
if (i + 1 >= count && symbol != ")")
{
}
else if (expression.ToString() != symbol)
{
expression.Append(symbol);
}
}
else if (expression.Length == 0 && symbol == "(")
{
expression.Append(symbol);
}
if (symbol == "days")
{
// calculating average values by days.
if (fromDate != null && toDate != null)
{
int days = toDate.Value.Subtract(fromDate.Value).Days + 1;
expression.Append(days);
}
else
{
expression.Append(1);
}
}
}
//Here is the code will have problem
if (expDic != null && expression != null)
{
expDic.Add(i, expression.ToString());
}
_sem.Release();
}), f);
taskList.Add(t);
}
多线程模式引起的，
那么我的代码有什么问题，我该如何解决？