Question

我在asp.net 3.5网页中有一个GridView控件，下面的代码在RowDataBound事件中执行，它改变了背景颜色和字体颜色，一旦列中的值：RegWaitTime和TotalWegTime大于30，

该值来自sql server中的两个计算列，它返回来自其他两列的减法结果，这里的问题是如果这些列中的值为NULL，我将得到更改代码的错误颜色，对不起我的英文，如果你需要我澄清我的要求，请告诉我，

提前致谢

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
     {



        // Change Wait Time Cell Rows  CHECK THE LOGIC HERE

        if (e.Row.RowType == DataControlRowType.DataRow)
         {
             // This line will get the reference to the underlying row
             DataRowView _row = (DataRowView)e.Row.DataItem;
             if (_row != null)
             {
                 // get the field value which you want to compare and
                 // convert to the corresponding data type
                 // i assume the fieldName is of int type
                 int _field = Convert.ToInt32(_row.Row["RegWaitTime"]);
                 if (_field > 30)
                 {
                     e.Row.Cells[9].BackColor = System.Drawing.Color.Red;
                     e.Row.Cells[9].Style.Add("color", "white");

                 }
                 else
                     e.Row.Cells[9].BackColor = System.Drawing.Color.Green;
                     e.Row.Cells[9].Style.Add("color", "white");
             }

         }


        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            // This line will get the reference to the underlying row
            DataRowView _row2 = (DataRowView)e.Row.DataItem;


            if (_row2 != null)
            {
                // get the field value which you want to compare and
                // convert to the corresponding data type
                // i assume the fieldName is of int type
                int _field = Convert.ToInt32(_row2.Row["TotalRegTime"]);
                if (_field > 30)
                {
                    e.Row.Cells[10].BackColor = System.Drawing.Color.Red;
                    e.Row.Cells[10].Style.Add("color", "white");

                }
                else
                    e.Row.Cells[10].BackColor = System.Drawing.Color.Green;
                    e.Row.Cells[10].Style.Add("color", "white");
            }
        }




     }

Answer 1

您需要将转换代码更改为：

int field=0;

if(int.TryParse(_row.Row["RegWaitTime"],out field))
{
    if(field>30)
    {
    }
}

您需要这样做的原因是，如果_row.Row["RegWaitTime"]为NULL，则您获得的实际值为DBNull.Value，Convert.ToInt32将InvalidCastException扼杀if (!DBNull.Value.Equals(_row.Row["RegWaitTime"])) { //then do the conversion as you are doing now. }因为对象不能从DBNull转换为其他类型。

另一种选择是：

{{1}}

Answer 2

检查数据库NULL，如下所示：

if(_row.Row["RegWaitTime"] != DBNull.Value)
{
    //change colour
{
else
{
    //do what you need to do when you get a NULL value
}

如何检查Gridview列中的空列

2 个答案: