在C＃中從DataTable檢索行時出錯

Question

問題 - 在MessageBox.Show("for loop, last row..."); //TEST CODE行之后出現錯誤MessageBox.Show("for loop, last row..."); //TEST CODE MessageBox.Show("for loop, last row..."); //TEST CODE執行。 可能是什么原因 ？ 當我從另一個數據庫獲取結果集時，沒有這樣的問題。 ：（ 我該如何解決 ？

代碼 -

    public void Main()
    {

        OleDbDataAdapter oleDA = new OleDbDataAdapter();
        DataTable dt = new DataTable();
        DataColumn col = null;
        DataRow row = null;
        string strCols = "";

        oleDA.Fill(dt, Dts.Variables["MyResultSet"].Value);
        col = dt.Columns["MyColumn"];

        int lastIdx = dt.Rows.Count - 1;

        MessageBox.Show("int declared, for loop..."); //TEST CODE

        //loop upto 2nd last data row
        for (int i = 0; i <= lastIdx-1; i++)
        {
            row = dt.Rows[i];
            strCols += row[col.Ordinal].ToString() + ", ";
        }

        MessageBox.Show("for loop, last row..."); //TEST CODE

        row = dt.Rows[lastIdx];
        strCols += row[col.Ordinal].ToString(); //!!! I GET ERROR HERE !

        MessageBox.Show("strCols");

        Dts.TaskResult = (int)ScriptResults.Success;

    }

錯誤 -

Error: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.IndexOutOfRangeException: There is no row at position -1.
   at System.Data.RBTree`1.GetNodeByIndex(Int32 userIndex)
   at System.Data.RBTree`1.get_Item(Int32 index)
   at System.Data.DataRowCollection.get_Item(Int32 index)
   at My-Long-Code-Goes-Here.csproj.ScriptMain.Main()
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
   at Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTATaskScriptingEngine.ExecuteScript()

Answer 1

我猜你的查詢沒有返回任何行。

檢查dt.Rows.Count ，驗證它是否> 0。

Answer 2

您正在嘗試使用沒有與之關聯的任何命令對象的采用者填充您的DataTable ，這就是為什么您將獲得空結果。 您需要創建一個命令對象，然后創建相關的DataAdapater ，然后使用Fill方法，如：

OleDbCommand selectCommand = new OleDbCommand("select * from yourTable", yourConnection);
OleDbDataAdapter oleDA = new OleDbDataAdapter(selectCommand);