如何将组合框的 selectedvalue 转换为整数？

Question

I have a combo box which was filled by datasource (value and id)

comboBox_Degree.DataSource = ds.Tables["Field"];`
comboBox_Degree.DisplayMember = "Field_Degree";
comboBox_Degree.ValueMember = "Field_ID";

now I want to retreive id when SelectedIndexChanged event occur. but when I cast it to an int I have such this error.

int fid = Convert.ToInt32(comboBox_Degree.SelectedValue.ToString());

error:

Input string was not in a correct format.

how can I cast this value to integer?

Answer 1

Use this:

int fid;
bool parseOK = Int32.TryParse(comboBox_Degree.SelectedValue.ToString(), out fid);

Answer 2

I usually do something like

int fid=0;
try {
     fid=int.Parse(comboBox_Degree.SelectedValue.ToString());
    } catch (Exception e)
    {
     //Whatever you want to do when it is not an int
    }

Answer 3

您可以使用此代码来解决您的问题：

 int id = Convert.ToInt32(comboBox_Degree.SelectedValue.GetHashCode());

Answer 4

I experienced the same problem and I found that setting the cbxExampleComboBox.DataSource first then setting the cbxExampleComboBox.ValueMember and cbxExampleComboBox.DisplayMember second is the reason why when you call cbxExampleComboBox.SelectedValue returns an object.

Setting the cbxExampleComboBox.ValueMember and cbxExampleComboBox.DisplayMember then cbxExampleComboBox.DataSource will return int if the type of cbxExampleComboBox.SelectedValue is int .

Changing the code to the following should return the result as int assuming that Field_ID is of int type

comboBox_Degree.ValueMember = "Field_ID";
comboBox_Degree.DisplayMember = "Field_Degree";
comboBox_Degree.DataSource = ds.Tables["Field"];

Answer 5

I was having a similar problem. However, the issue was due to the combobox setup phase firing the eventhandler. So, I moved the SelectedIndexChanged EventHandler add from the Form.Designer to the FormLoad Event after the combobox setup (DataSource, ValueMember and DisplayMember assignments).

  // Example Combobox for Roles
  DataTable dtRoles = new DataTable();
  dtRoles = labDAO.GetRoles();
  cbxRoleID.DataSource = dtRoles;
  cbxRoleID.ValueMember = "ID";
  cbxRoleID.DisplayMember = "Name";
  cbxRoleID.SelectedIndexChanged += cbxRoleID_SelectedIndexChanged;