Question

Visual C# 2008 Express. Access 2010 database. When I use the following code I receive an error ‘Data type mismatch in criteria expression’, but if I take out the code for the txt85x11bw_Validating event it works just fine. I’m trying to understand how there is a date type mismatch.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;

namespace GISReciepts
{
public partial class GISReceipts : Form
{
    public GISReceipts()
    {
        InitializeComponent();
    }

    private void cmdExit_Click(object sender, EventArgs e)
    {
        this.Close();
    }

    private void cmdAdd_Click(object sender, EventArgs e)
    {
        string strSQL = "INSERT INTO Table1(Name1, Date1, CollectedBy, 85x11BW) VALUES(@Name, @Date, @CollectedBy, @85x11BW)";

        //OleDbConnection is a class that represents an open connection to a data source
        OleDbConnection myConnection = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Temp\\GISTest.accdb");
        //OleDbCommand is a class that represents an SQL statement or stored procedure to execute against a data source.(takes care of passing queries to the database.
        OleDbCommand myCommand = new OleDbCommand(strSQL, myConnection);
        myCommand.Parameters.AddWithValue("@Name", txtName.Text);
        myCommand.Parameters.AddWithValue("@Date", maskedTextBoxDate.Text);
        myCommand.Parameters.AddWithValue("@CollectedBy", txtCollectedBy.Text);
        myCommand.Parameters.AddWithValue("@85x11BW", txt85x11bw.Text);

        try
        {
            myConnection.Open();
            myCommand.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
        finally
        {
            myConnection.Close();
           // MessageBox.Show("Entry Added");  //this is displaying even on errors & when no data is added to table
        }

    }

    private void GISReceipts_Load(object sender, EventArgs e)
    {
        maskedTextBoxDate.Text = DateTime.Today.ToString("MM/dd/yyyy");

        txt85x11bw.Validating += new CancelEventHandler(txt85x11bw_Validating);       
    }


    private void GISReceipts_FormClosing(object sender, FormClosingEventArgs e)
    {
        DateTime value;
        //DateTime.TryParse converts the srting representation of a date to its DateTime equivalent & returns a value that indicates whether the conversion succedded.
        if (!DateTime.TryParse(maskedTextBoxDate.Text, out value))
        {
            maskedTextBoxDate.Text = DateTime.Today.ToShortDateString();
        }

    }

    private void txt85x11bw_Validating(object sender, CancelEventArgs e)
    {
        if (string.IsNullOrEmpty(txt85x11bw.Text))
        {
            //do nothing
        }
        else
        {
            //initialize the variable numberEntered of type int
            int numberEntered;

            //int=integer TryParse=method that converts strings into integer (value, out result)
            if (int.TryParse(txt85x11bw.Text, out numberEntered))
            {
                //if number is less than 1 or more than 1,000
                if (numberEntered < 1 || numberEntered > 1000)
                    MessageBox.Show("You must enter a valid number");
                txt85x11bw.Clear();

            }
            //if conversion failed
            else
            {
                MessageBox.Show("You must enter a number");
                txt85x11bw.Clear();

            }
        }


    }

}

}

Answer 1

This line adds a parameter with a datatype text, instead, I assume, that in your database the column 85x11BW is of numeric type (an int looking at your validating code)

    myCommand.Parameters.AddWithValue("@85x11BW", txt85x11bw.Text);

try to change the line in this way

    myCommand.Parameters.AddWithValue("@85x11BW", Convert.ToInt32(txt85x11bw.Text));

in this way you force the AddWithValue method to add a parameter with its DbType property set to Int32. You could have the same problem for the parameter @Date, if the relative datatable column is of DateTime type.

EDIT If the txt85x11BW is empty you need to decide which default value you accept for that column in the datatable. If you accept a NULL you could write something like this

        int numberEntered = 0;
        int.TryParse(txt85x11bw.Text, out numberEntered);
        if (numberEntered >= 1 && numberEntered <= 1000)
             myCommand.Parameters.AddWithValue("@85x11BW", numberEntered);
        else
             myCommand.Parameters.AddWithValue("@85x11BW", DBNull.Value);

EDIT 2 In the validating event the code clears the content of the maskedit also if the value is correct. You need braces after the condition

if (int.TryParse(txt85x11bw.Text, out numberEntered))
{
    //if number is less than 1 or more than 1,000
    if (numberEntered < 1 || numberEntered > 1000)
    {
        MessageBox.Show("You must enter a valid number");
        txt85x11bw.Clear();
    }
}