解决错误...无法将参数值从ListItem转换为String。 [英] solve error...Failed to convert parameter value from a ListItem to a String.
问题描述
我希望使用三个下拉列表将日期值插入表中,但错误显示
错误: - 无法将参数值从ListItem转换为String。
代码如下: -
protected void Button2_Click(object sender,EventArgs e)
{
string image = FileUpload1.FileName;
string ext = image.Substring(image.LastIndexOf(。));
if(ext.ToLower()==.jpg|| ext.ToLower()==。jpeg|| ext.ToLower()= =。gif)
{
FileUpload1.SaveAs(MapPath(images \\)+ image);
path1 = @images /+ image;
}
string date = DropDownList1.SelectedValue.ToString()+ - + DropDownList2.SelectedValue.ToString()+ - + DropDownList3.SelectedValue.ToString();
con .Open();
SqlCommand cmd = new SqlCommand(instud,con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Connection = con;
cmd.Parameters.Add(@ date,SqlDbType.VarChar,50).Value = TextBox1.Text;
cmd.Parameters.Add(@ name,SqlDbType.VarChar,50).Value = TextBox2.Text;
cmd.Parameters.Add(@ gendr,SqlDbType.VarChar ,50).Value = RadioButtonList1.SelectedItem;
错误: - cmd.Parameters.Add(@ dob,SqlDbType.VarChar,50).Value = date;
cmd.Parameters.Add(@ fnam,SqlDbType.VarChar,50).Value = TextBox5.Text;
cmd.Parameters.Add(@ focc,SqlDbType.VarChar,50) .Value = TextBox6.Text;
cmd.Parameters.Add(@ pradd,SqlDbType.VarChar,100).Value = TextBox7.Text;
cmd.Parameters .Add(@ padd,SqlDbType.VarChar,100).Value = TextBox8.Text;
cmd.Parameters.Add(@ m ob,SqlDbType.VarChar,50).Value = TextBox9.Text;
cmd.Parameters.Add(@ cid,SqlDbType.Int).Value = TextBox10.Text;
cmd.Parameters.Add(@ cnam,SqlDbType.VarChar,50).Value = TextBox11.Text;
cmd.Parameters.Add(@ duration,SqlDbType.VarChar ,50).Value = TextBox12.Text;
cmd.Parameters.Add(@ catgy,SqlDbType.VarChar,50).Value = TextBox13.Text;
cmd.Parameters.Add(@ img,SqlDbType.VarChar,50).Value = path1;
cmd.ExecuteNonQuery();
cmd.Dispose();
con.Close();
clear();
Label15.Visible = true;
Label15。 Text =成功插入记录;
}
i want date value insert into table using three dropdownlist but error show
error:-Failed to convert parameter value from a ListItem to a String.
code following:-
protected void Button2_Click(object sender, EventArgs e)
{
string image = FileUpload1.FileName;
string ext = image.Substring(image.LastIndexOf("."));
if (ext.ToLower() == ".jpg" || ext.ToLower() == ".jpeg" || ext.ToLower() == ".gif")
{
FileUpload1.SaveAs(MapPath("images\\") + image);
path1 = @"images/" + image;
}
string date = DropDownList1.SelectedValue.ToString() + "-" + DropDownList2.SelectedValue.ToString() + "-" + DropDownList3.SelectedValue.ToString();
con.Open();
SqlCommand cmd = new SqlCommand("instud", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Connection = con;
cmd.Parameters.Add("@date", SqlDbType.VarChar, 50).Value = TextBox1.Text;
cmd.Parameters.Add("@name", SqlDbType.VarChar, 50).Value = TextBox2.Text;
cmd.Parameters.Add("@gendr", SqlDbType.VarChar, 50).Value = RadioButtonList1.SelectedItem;
ERROR:- cmd.Parameters.Add("@dob", SqlDbType.VarChar, 50).Value =date;
cmd.Parameters.Add("@fnam", SqlDbType.VarChar, 50).Value = TextBox5.Text;
cmd.Parameters.Add("@focc", SqlDbType.VarChar, 50).Value = TextBox6.Text;
cmd.Parameters.Add("@pradd", SqlDbType.VarChar, 100).Value = TextBox7.Text;
cmd.Parameters.Add("@padd", SqlDbType.VarChar, 100).Value = TextBox8.Text;
cmd.Parameters.Add("@mob", SqlDbType.VarChar, 50).Value = TextBox9.Text;
cmd.Parameters.Add("@cid", SqlDbType.Int).Value = TextBox10.Text;
cmd.Parameters.Add("@cnam", SqlDbType.VarChar, 50).Value = TextBox11.Text;
cmd.Parameters.Add("@duration", SqlDbType.VarChar, 50).Value = TextBox12.Text;
cmd.Parameters.Add("@catgy", SqlDbType.VarChar, 50).Value = TextBox13.Text;
cmd.Parameters.Add("@img", SqlDbType.VarChar, 50).Value = path1;
cmd.ExecuteNonQuery();
cmd.Dispose();
con.Close();
clear();
Label15.Visible = true;
Label15.Text = "Insert Record Successfully";
}
推荐答案
1.您不必转换字符串DropDownList
对象的属性SelectedValue
,因为它们是字符串。此属性返回所选项的值,如果未选择任何项,则返回sting.Empty
。
2.RadioButtonList1
对象的属性SelectedItem
默认返回null
value,如果未选择列表中的单选按钮,则尝试将null
值转换为字符串时会生成错误。
3.解决方案是管理这种情况(当值可能是null
)并且你有执行此操作的选项:
i)在页面初始化时设置RadioButtonList1的默认值(在Page_Load
时IsPostBack
为false);这是我推荐的选项!
ii)在上面的代码中测试,如果为null则设置一个有效值(如0或1);
1.You do not have to convert to string the propertySelectedValue
of yourDropDownList
objects, because they are strings. This property returns the value of the selected item, and if no item is selected it returnssting.Empty
.
2.The propertySelectedItem
of yourRadioButtonList1
object returns by defaultnull
value, if no radio button from the list is selected, so the error is generated by the trying to convertnull
value to string.
3.The solution is to manage also this case (when the value could benull
) and you have to options for doing this:
i)to set a default value of your RadioButtonList1 when the page is initialized (in yourPage_Load
whenIsPostBack
is false); This is the option that I recommend!
ii)to test in your code above, and if is null to set one valid value (like "0" or "1");
将RadioButtonList1.SelectedItem;
转换为有效的varchar
值(例如0或1,Y或N等)在将其发送到存储过程之前。
ConvertRadioButtonList1.SelectedItem;
to a validvarchar
value (e.g. 0 or 1, Y or N etc) before sending it to the stored procedure.
更改此行代码
change this line of code
cmd.Parameters.Add("@gendr", SqlDbType.VarChar, 50).Value = RadioButtonList1.SelectedItem;
to
to
cmd.Parameters.Add("@gendr", SqlDbType.VarChar, 50).Value = RadioButtonList1.SelectedItem.Value;
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