输入的字符串格式不正确

Question

Anyone Please help....

Error -

Input string was not in a correct format.

int comboxchoice = Int32.Parse(comboBox1.SelectedValue.ToString());

i am using below code

private void Form2_Load(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection(@"Data Source=MANISH-PC\SQLEXPRESS;Initial Catalog=test2.mdf;Integrated Security=True");
            conn.Open();
            SqlCommand command = new SqlCommand("select * from table1", conn);
            SqlDataAdapter adp = new SqlDataAdapter(command);
            tbl = new DataTable();
            adp.Fill(tbl);
            comboBox1.DataSource = tbl;
            comboBox1.ValueMember = tbl.Columns[0].ColumnName;
            comboBox1.DisplayMember = tbl.Columns[0].ColumnName;
      }
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection(@"Data Source=MANISH-PC\SQLEXPRESS;Initial Catalog=test2.mdf;Integrated Security=True");
            conn.Open();
            SqlCommand command = new SqlCommand("select name from table1 where id=@id", conn);
            int comboxchoice = Int32.Parse(comboBox1.SelectedValue.ToString());
           command.Parameters.AddWithValue("@id",comboxchoice);
             SqlDataAdapter adp = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adp.Fill(ds, "table1");
            textBox1.Text = ds.Tables["table1"].Rows[0]["name"].ToString();
           }
    }

Answer 1

I couldn't see which method you do need but the error you are receiving is because SelectedValue is returning a DataView (according to your comment).

According to the Msdn documentation for DataView , under ToString,

Returns a String containing the name of the Component

As a start you can try casting

(DataView)comboBox.SelectedValue

But this should include extra error handling to ensure that SelectedValue is a valid DataView.

---

As a side note, you ccould also avoid this with better number parsing

int comboChoice;
if(int.TryParse((DataView)comboBox.SelectedValue, out comboChoice))
   //Do something
else
    //Number invalid, do something else

Answer 2

Because comboBox1.SelectedValue is not returning a correct integer value.

You success to change comboBox1.SelectedValue to string, but the string cannot convert to corresponding integer because it is not integer .

For example, the following statement triggers same error

        //non-integer
        string omg = "2313asd";
        int convertedINT = Int32.Parse(omg.ToString());

Get idea from @Vignesh Kumar, empty string is not recognize as integer format also.

        //empty string
        string omg = "";
        int convertedINT = Int32.Parse(omg.ToString());

If you confirm only empty string triggers your error , then only check for the empty string with string.IsNullOrEmpty()

if you want to eliminate the error totally , then confirm your comboBox1.SelectedValue is correct integer format with Int32.TryParse() .

        int comboxchoice;
        if (Int32.TryParse(comboBox1.SelectedValue.ToString(), out comboxchoice))
        {
            proceed by using comboxchoice as converted int value
        }
        else
        {
            //not integer value.....
        }

or Maybe you can display the string can check if it is integer value as you imagine

        MessageBox.Show(comboBox1.SelectedValue.ToString());

Answer 3

Can't you get rid of the "ToString()". I believe the "SelectedValue" itself is a string value.