“将数据类型 nvarchar 转换为 int 时出错”

Question

In this part of my app I am trying to do a invoice generator where it requires certain information. First of all it has an auto-generated Id, then we have some other infos just as: the date, the name of a student and the month that you want to pay, all the fields mentioned before have to be selected from a dropdown list of its types. And then we have some other data such as the amount, the ncf and rnc things that must be written by the cashier.

I've been trying to solve this issue in many ways but I can't really find a way to do it. I've been trying parsing and some other crazy ideas that came to my mind but none of those worked.

Here's the code:

private void SaveStudentFee()
{
    try
    {
        command = new SqlCommand("uspStudentFee", connection);
        command.CommandType = CommandType.StoredProcedure;
        connection.Open();
        command.Parameters.AddWithValue("@Action", (UpdateMode) ? "Update" : "Insert");
        command.Parameters.AddWithValue("@FeeID", txtFeeID.Text);
        command.Parameters.AddWithValue("@FKStudentID", CB_StdFee.Text);
        command.Parameters.AddWithValue("@FeeDate", DT_FeePayDate.Value);
        command.Parameters.AddWithValue("@FeeRNC",txtRNC.Text);
        command.Parameters.AddWithValue("@FeeNCF",txtNCF.Text);
        command.Parameters.AddWithValue("@Fees", Txt_Fee.Text);
        command.Parameters.AddWithValue("@FeeMonth", CB_PayMonth.Text);
        command.ExecuteNonQuery();
    catch (Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }
    finally
    {
        connection.Close();
    }
}

Here's the stored procedure:

create PROC uspStudentFee
    @Action NVARCHAR(50),
    @FeeID INT=NULL,
    @FKStudentID INT=NULL,
    @FeeDate DATE=NULL,
    @FeeRNC NVARCHAR(50)=NULL,
    @FeeNCF NVARCHAR(50)=NULL,
    @Fees NVARCHAR(50)=NULL,
    @FeeMonth INT=NULL

Answer 1

Given you are grabbing your stored procedure inputs from what appears to be some sort of input fields, double check the formatting of your numbers. For instance, check txtFeeID , CB_StdFee , CB_PayMonth to make sure that they are not represented as a decimal. As an example 100.00 is a valid number, but the decimal cannot be parsed, so it would most certainly cause the conversion error. I'd add Convert.ToInt32() to all of your Integer fields.