Opening, Reading, and Writing a file

Here is an example of Opening/Reading a file in btnOpen_Click and Writing in btnSave_Click:

    protected void btnOpen_Click(object sender, EventArgs e)
    {
        if (string.IsNullOrEmpty(txtFileName.Text)) txtFileName.Text="c:/temp/temp.txt";
        StreamReader sr = null;
        try
        {
            sr = new StreamReader(txtFileName.Text);
            txtFileContent.Text = sr.ReadToEnd();
            sr.Close();
            displayMessage("Successfully opened file");
        }
        catch (Exception ex)
        {
            displayMessage(ex.Message);
        }
        finally
        {
            sr.Close();
        }
    }
    protected void btnSave_Click(object sender, EventArgs e)
    {
        if (string.IsNullOrEmpty(txtFileName.Text)) txtFileName.Text = "c:/temp/temp.txt";
        StreamWriter sw = null;
        try{
            sw = new StreamWriter(txtFileName.Text);
            string[] ar;
            ar = txtFileContent.Text.Split(Environment.NewLine.ToCharArray());
            foreach (string sIn in ar)
            {
                if(!string.IsNullOrEmpty(sIn))
                    sw.Write(sIn.Trim()+Environment.NewLine);
            }
        }catch (Exception ex) 
        {
            displayMessageLine(ex.Message);
        }
        finally{
            sw.Close();
        }
    }

Using a nullable boolean.

It is possible to assign a nullable boolean in C#. The trick is to use ? in the declaration. Once declared, one can use the HasValue() method. An example follows:

    protected void Page_Load(object sender, EventArgs e)
    {
        bool? isUser = null;
        lblStatus.Text = isUser.HasValue.ToString(); //displays false
        // an int example: Nullable<int> i = null;
    }
    protected void btnCheckStatus_Click(object sender, EventArgs e)
    {
        bool? isUser = false;
        lblStatus.Text = isUser.HasValue.ToString(); //displays true
    }

Clearing controls in GridView row using delete

Here is how to clear controls in GridView row using delete. Be careful that GridViewDeleteEventArgs is not GridViewDeletedEventArgs!

                                <asp:GridView ID="gvStolenStatusInfo" runat="server" AutoGenerateColumns="false" AllowPaging="true"
                                    EmptyDataText="No records found." PageSize="10" CssClass="gridView"
                                    OnRowDeleting="gvStolenStatusInfo_RowDeleting" AutoGenerateDeleteButton="true">
                                    <Columns>
                                        <asp:TemplateField HeaderText="Status">
                                            <ItemTemplate>
                                                <asp:TextBox ID="txtuCode" runat="server" Text='<%# Bind("Code") %>' />
                                            </ItemTemplate>
                                        </asp:TemplateField>
                                        <asp:TemplateField HeaderText="Comment">
                                            <ItemTemplate>
                                                <asp:TextBox ID="txtuComment" runat="server" Text='<%# Bind("Comment") %>' />
                                            </ItemTemplate>
                                        </asp:TemplateField>
                                    </Columns>
                                </asp:GridView> 

Notice the OnRowDeleting set to x_RowDeleting function and AutoGenerateDeleteButton. Now for the delete function:

    protected void gvStolenStatusInfo_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        int rowID = e.RowIndex;
        ((TextBox)gvStolenStatusInfo.Rows[rowID].FindControl("txtuCode")).Text = string.Empty;
        ((TextBox)gvStolenStatusInfo.Rows[rowID].FindControl("txtuDate")).Text = string.Empty;
    }

References: http://www.codeproject.com/KB/webforms/Editable_GridView.aspx

Multiple PostBack problem with GridView

I noticed my SelectedIndexChanged method being called twice in IE7 when I selected a gridview row. I used solution 2 at http://www.codeproject.com/KB/aspnet/GVImageCommandButtonProb.aspx to solve the problem.

Resetting a StringBuilder

Here is how to reset a StringBuilder:

myStringBuilder.Length = 0;

myStringBuilder.Remove(0, myStringBuilder.Length) also works, but why bother with that one?
References: http://forums.asp.net/t/1193708.aspx

Creating a GUID from scatch

Sometimes you might want a psuedo-random string value. This can be done with:
System.Guid.NewGuid().ToString();

Changing the default login page for use with LoginStatus control

Sometimes it is desirable to have a different default login page. For example, a simple site where administrators login at http://foo.com/admin/Login.aspx versus the standard http:foo.com/Login.aspx. The LoginStatus control will hyperlink back to the default login page. To change this default login page, change the web.config file as follows:

    <authentication mode="Forms" >
      <forms loginUrl="~/admin/Login.aspx"></forms>
    </authentication>

Reference: http://erlend.oftedal.no/blog/?blogid=55