C# 找不到第4列

早上好，当我试图通过C中的select使用表列时，我很难克服这个问题。我可以获取该值并将其放入text.box3中，但真正的目的是将该值用作图表中的X

错误中出现的值4是我要插入的列的值之一。这意味着查询正在运行，我用来获取这些值的方式​​从列中可以看出，这是不正确的。无法在变量中使用查询数据？所以我可以用这个变量把它插入图表

这是我得到的例外：

  [IndexOutOfRangeException: Não é possível localizar a coluna 4.]
  System.Data.DataColumnCollection.get_Item(Int32 index) +79
  System.Web.UI.DataVisualization.Charting.DataPointCollection.GetValueType
  (IEnum
  erator enumerator, String field) +918    
  System.Web.UI.DataVisualization.Charting.DataPointCollection.
  AutoDetectValues
  Type(Series series, IEnumerator xEnumerator, String xField, IEnumerator 
  yEnumerator, String yField) +25
  System.Web.UI.DataVisualization.
  Charting.ChartImage.DataBind(IEnumerable dataSource, ArrayList seriesList) 
  +1089
  System.Web.UI.DataVisualization.Charting.Chart.
  PerformDataBinding(IEnumerable 
  data) +21 
  System.Web.UI.WebControls.DataBoundControl.
  OnDataSourceViewSelectCallback(IEnume
  rable data) +128
  System.Web.UI.DataSourceView.Select
  (DataSourceSelectArguments arguments, 
  DataSourceViewSelectCallback callback) +34
  System.Web.UI.WebControls.DataBoundControl.PerformSelect() +143
  System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +74
  System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +114
  System.Web.UI.WebControls.BaseDataBoundControl.OnPreRender(EventArgs e) 
  +22
  System.Web.UI.Control.PreRenderRecursiveInternal() +88
  System.Web.UI.Control.PreRenderRecursiveInternal() +160
  System.Web.UI.Control.PreRenderRecursiveInternal() +160
  System.Web.UI.Page.ProcessRequestMain(Boolean           
  includeStagesBeforeAsyncPoint, 
  Boolean includeStagesAfterAsyncPoint) +883a

代码如下：

    String connectionString =
    "Data Source=localhost;" +
    "Initial Catalog=DB_SACC;" +
    "User id=sa;" +
    "Password=1234;";
    decimal average = 0;
    SqlConnection connection = new SqlConnection(connectionString);

    SqlCommand cmd = new SqlCommand();

    string teste = "SELECT (Consumo_Medio_Real)AS 'cmr' FROM t_faturas";

    cmd.CommandText = teste;

    connection.Open();

    cmd.Connection = connection;

    cmd.CommandType = CommandType.Text;

    using (var reader = cmd.ExecuteReader())
    {
        while (reader.Read())
        {

            average = Convert.ToDecimal(reader["cmr"].ToString());
            TextBox3.Text = average.ToString();
            break;
        }
        Chart1.Series["Series1"].YValueMembers = "Estimativa";
        Chart1.Series["Series1"].XValueMember = average.ToString();
    }

---

您的问题是：在查询时从“cmr”中删除“while loop”。如果在第一次迭代时中断，为什么需要while循环？如果我删除crm，我应该在阅读器中放置什么？@Berkayit是真的，我不需要它，谢谢@Reniuz