c#验证错误

本文关键字：错误 验证 | 更新日期: 2023-09-27 18:10:48

嘿，我是c#新手，我相信这不是一个太难的问题，但是我无法理解它。

我有一个方法，在这个方法中，我从一个windows窗体中检索所有变量，并将它们提交到另一个方法中，该方法将它们插入到数据库中。当变量被声明时，它的工作很好，但是当我尝试添加一点验证来检查空值时，我收到一个"名称'gridRef1V'不存在于当前上下文中"的错误。

我现在的验证是，

if (cbGridRef1.SelectedValue != null)
        {
            string gridRef1V = cbGridRef1.SelectedValue.ToString();
        }
        else
        {
            MessageBox.Show("The grid ref1 field must contain a value");
            cbGridRef1.Focus();
        }

接收错误消息的代码行是，

SQLMethods.inspectionInsert(scrapTypeV, scrapShiftV, scrapDateV, prodAreaV, castDateV, dieNoV, dieCodeV, dieDescV, machineV, casterIDV, castShiftV, fettlerIDV, scrapCodeV, scrapTotalV, partIDV, gridRef1V, gridRef2V, qtyScrapV);

感谢您的帮助。

c#验证错误

您有一个作用域错误。

移动
string gridRef1V;

在if语句之外。

在if语句中，该变量在代码块之外不可用。

    // gridRef1v doesn't exist
    if (cbGridRef1.SelectedValue != null)
    {
        string gridRef1V = cbGridRef1.SelectedValue.ToString();
    }  //gridRef1V no longer available after this } 
    else
    {
        // gridRef1v doesn't exist
        MessageBox.Show("The grid ref1 field must contain a value");
        cbGridRef1.Focus();
    }
    // gridRef1v doesn't exist

你想要的更像是:

    string gridRef1v;
    if (cbGridRef1.SelectedValue != null)
    {
       gridRef1V = cbGridRef1.SelectedValue.ToString();
    }  //gridRef1V still available after this } 
    else
    {
        // gridRef1v exists
        MessageBox.Show("The grid ref1 field must contain a value");
        cbGridRef1.Focus();
    }
    // gridRef1v exists

尝试:

string gridRef1V;
if (cbGridRef1.SelectedValue != null)
        {
            gridRef1V = cbGridRef1.SelectedValue.ToString();
        }
        else
        {
            MessageBox.Show("The grid ref1 field must contain a value");
            cbGridRef1.Focus();
        }

你必须在if块的作用域之外声明gridRef1V才能在其他地方使用它

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