Data type mismatch in criteria expression while deleting record from gridview in asp.net

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designed page code of gridview in asp.net

ASP.NET

<asp:GridView ID="GridView1" runat="server" Width="100%" AutoGenerateColumns="False" DataKeyNames="SID" BackColor="White" BorderColor="#CCCCCC" BorderStyle="None" BorderWidth="1px" CellPadding="3" OnRowCancelingEdit="GridView1_RowCancelingEdit" OnRowDeleting="GridView1_RowDeleting" OnRowEditing="GridView1_RowEditing" OnRowUpdating="GridView1_RowUpdating">
                        <Columns>
                            <asp:BoundField DataField="SID" HeaderText="SID" InsertVisible="False" ReadOnly="True" SortExpression="SID" />
                            <asp:BoundField DataField="StudentName" HeaderText="StudentName" SortExpression="StudentName" />
                            <asp:BoundField DataField="Gender" HeaderText="Gender" SortExpression="Gender" />
                            <asp:BoundField DataField="ParentName" HeaderText="ParentName" SortExpression="ParentName" />
                            <asp:BoundField DataField="MobileNo" HeaderText="MobileNo" SortExpression="MobileNo" />
                            <asp:BoundField DataField="Class" HeaderText="Class" SortExpression="Class" />
                            <asp:BoundField DataField="PickUpPoint" HeaderText="PickUpPoint" SortExpression="PickUpPoint" />
                            <asp:BoundField DataField="BusStatus" HeaderText="BusStatus" SortExpression="BusStatus" />
                            <asp:BoundField DataField="BusFees" HeaderText="BusFees" SortExpression="BusFees" />
                            <asp:BoundField DataField="TutionFees" HeaderText="TutionFees" SortExpression="TutionFees" />
                            <asp:BoundField DataField="StationaryFees" HeaderText="StationaryFees" SortExpression="StationaryFees" />
                            <asp:BoundField DataField="OtherFee" HeaderText="OtherFee" SortExpression="OtherFee" />
                            <asp:BoundField DataField="TotalFees" HeaderText="TotalFees" SortExpression="TotalFees" />
                            <asp:BoundField DataField="PaidFees" HeaderText="PaidFees" SortExpression="PaidFees" />
                            <asp:BoundField DataField="Remaining" HeaderText="Remaining" SortExpression="Remaining" />
                            <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" />
                        </Columns>
                        <FooterStyle BackColor="White" ForeColor="#000066" />
                        <HeaderStyle BackColor="#006699" Font-Bold="True" ForeColor="White" />
                        <PagerStyle BackColor="White" ForeColor="#000066" HorizontalAlign="Left" />
                        <RowStyle ForeColor="#000066" />
                        <SelectedRowStyle BackColor="#669999" Font-Bold="True" ForeColor="White" />
                    </asp:GridView>

c# code:

C#

protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
 {
     int i = e.RowIndex;
     DataKey dk = GridView1.DataKeys[i];
     con.Open();
     OleDbCommand cmd = new OleDbCommand("delete from StudentDetails where SID='" + Convert.ToInt16(dk.Value) + "'", con);

     cmd.ExecuteNonQuery();
     con.Close();
     bind();

 }

error occurring on cmd.executenonquery:
An exception of type 'System.Data.OleDb.OleDbException' occurred in System.Data.dll but was not handled in user code

Additional information: Data type mismatch in criteria expression

Posted 25-Nov-15 3:50am

Member 10234718

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3 solutions

Solution 3

Check the datatype of column SID in table StudentDetails. It may be Integer type. if it is integer type then no need to give it as string type.

Posted 25-Nov-15 22:50pm

manu027

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Richard Deeming · Accepted Answer · 2015-11-25T05:26:00

NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query. If you don't, you'll leave your code vulnerable to SQL Injection[^].

In this particular case, since you have converted the parameter to a number, it's unlikely that anyone could exploit it. However, it's a good idea to get into the habit of always using parameters, so that you don't miss a potentially-exploitable vulnerability.

Also, it looks like you're storing the connection in a field. That's not a good idea. You should create the connection as late as possible, and dispose of it as soon as you're finished using it.

C#

private static OleDbConnection CreateConnection()
{
    return new OleDbConnection("....");
}

protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
    int i = e.RowIndex;
    DataKey dk = GridView1.DataKeys[i];
    
    using (OleDbConnection con = CreateConnection())
    using (OleDbCommand cmd = new OleDbCommand("delete from StudentDetails where SID = ?", con))
    {
        // OleDb doesn't use named parameters, so only the order matters here:
        cmd.Parameters.AddWithValue("SID", dk.Value);
        
        con.Open();
        cmd.ExecuteNonQuery();
    }
    
    bind(); 
}

Manas_Kumar · Accepted Answer · 2015-11-25T04:13:00

Solution 1

Most probably SID column is integer in StudentDetails table. But in query SID is used as text data. So it is throwing data type mismatch. Code should like below:

C#

OleDbCommand cmd = new OleDbCommand("delete from StudentDetails where SID=" + Convert.ToInt16(dk.Value) + "", con);

Posted 25-Nov-15 4:13am

Manas_Kumar

Updated 25-Nov-15 22:12pm

v2