将float数据类型列转换为双精度时出错

Question

下面的代码给出了错误：指定的转换无效。

protected void gridview1_RowDataBound(object sender, GridViewRowEventArgs e) 
    { 
     if (e.Row.RowType == DataControlRowType.DataRow) 
     { 
      DataRow row = ((DataRowView)e.Row.DataItem).Row; 
      **double Yellow = Convert.ToDouble(row.Field<float?>("Yellow"));** 
     } 
    }  

下面的代码适用于我。但我无法在下面的代码

double Yellow = Convert.ToDouble(((DataRowView)e.Row.DataItem)["Yellow"]); 

请帮忙处理NULL值..

Answer 1

尝试将它们分成多行以避免破坏得墨忒耳定律。它会使阅读更容易。

var dataRowView = e.Row.DataItem as DataRowView; 
DataRow row = dataRowView.Row; 
var result = (row["Yellow"] as double?) ?? 0.0; 

Answer 2

尝试使用

double? Yellow = ((DataRowView)e.Row.DataItem)["Yellow"] != null ? Convert.ToDouble(((DataRowView)e.Row.DataItem)["Yellow"]) : (double?)null; 

Answer 3

最后，我不得不使用System.DBNull.Value检查

if (((DataRowView)e.Row.DataItem)["Yellow"] != System.DBNull.Value) 
      { 
       double? Yellow = 
        (double?)Convert.ToDouble(((DataRowView)e.Row.DataItem)["Yellow"]); 
      }