C# Gridview中的文本框返回null或'；System.Web.UI.WebControls.TextBox'；

我在从文本框检索数据时遇到问题。文本框位于Gridview中。我试着调试，结果显示我收集textbox值的变量返回

null

或

System.Web.UI.WebControls.textbox

你能帮我弄清楚是什么问题吗

下面是来自后端和gridview的代码

public void Button_Submit_Onclick(object sender, EventArgs e)
{
    for (int i = 0; i < GridView2.Rows.Count; i++)
    {
        //Textbox from Gridview
        TextBox txt_field = (TextBox)GridView2.Rows[i].Cells[12].FindControl("txt_Comment");
        //Connection string
        con.ConnectionString = ConfigurationManager.ConnectionStrings["TestDeductionsConnectionString2"].ToString();
        //id of column
        int recordid = Convert.ToInt32(GridView2.DataKeys[i].Values[0]);
        //checkbox value
        CheckBox cbox = (CheckBox)GridView2.Rows[i].FindControl("CheckBox1");
        bool private1 = Convert.ToBoolean(cbox.Checked); 
        //open connection and creating sqlcommand
        SqlCommand cmd = new SqlCommand();
        cmd.Connection = con;
        con.Open();
        cmd.CommandText = "Update DetailCosts set private='" + private1 + "' Komentar='" + txt_field + "'  where recordid=" + recordid;
        //
        cmd.Parameters.AddWithValue("@private1", SqlDbType.Bit).Value = private1;
        cmd.Parameters.AddWithValue("@recordid", SqlDbType.Int).Value = recordid.ToString();
        cmd.Parameters.AddWithValue("@Komentar", SqlDbType.NChar).Value = txt_field.ToString();               
        cmd.ExecuteNonQuery();

        if (private1==true)
        {
            //DateTime date = DateTime.Now;
            //cmd.CommandText = "Update AprovedCosts set AprovedCosts.AprovalUser = ";

            cmd.CommandText = "Update DetailCosts set privateCost=Costs where recordid=" + recordid;
            cmd.ExecuteNonQuery();
        }
        else
        {

            cmd.CommandText = "Update DetailCosts set privateCost=0 where recordid=" + recordid;
            cmd.ExecuteNonQuery();
        }
        con.Close();
    }
}

public void按钮\u Submit\u Onclick（对象发送方，事件参数e）
{
对于（int i=0；i

Gridview：

<asp:TemplateField HeaderText="Comment">
    <ItemTemplate>
        <asp:TextBox ID="txt_Comment" runat="server" Text='<%# Eval("Komentar") %>'></asp:TextBox>
    </ItemTemplate>
</asp:TemplateField>

尝试使用

txt\u field.Text

而不是

txt\u field.ToString（）

来获取值。

您正在搜索可能不存在的控件，并将其分配给文本框控件

TextBox txt_field = (TextBox)GridView2.Rows[i].Cells[12].FindControl("txt_Comment");

为什么不将textbox.text值指定给GridView2.Rows[i].Cells[12].text

---

它将返回一个值，假设它存在。

要使它更简单，只需像这样使用它

TextBox txt_field = (TextBox)GridView2.Rows[i].Cells[12].FindControl("txt_Comment");
string txt = txt_field.text; //store it's text in string

并更改

命令

代替

txt_字段

只需编写txt或

txt.ToString（）

但是System.Web.UI.Control不包含文本方法，我不能使用它
 cmd.CommandText = "Update DetailCosts set private='" + private1 + "' Komentar='" + txt + "'  where recordid=" + recordid;
    //
    cmd.Parameters.AddWithValue("@private1", SqlDbType.Bit).Value = private1;
    cmd.Parameters.AddWithValue("@recordid", SqlDbType.Int).Value = recordid.ToString();
    cmd.Parameters.AddWithValue("@Komentar", SqlDbType.NChar).Value = txt.ToString();