Using a GridView with Edit and Delete that use stored procedures

Here is how to use a GridView with Edit and Delete that use stored procedures for update and delete. First, the aspx:

        <asp:GridView ID="gvEmail" runat="server" AutoGenerateDeleteButton="True" 
        AutoGenerateEditButton="True" AutoGenerateColumns="False" DataSourceID="SqlDataSource1"
        AllowPaging="True" OnRowDeleting="gvEmail_RowDeleting" PageSize="99" OnRowUpdating="gvEmail_OnRowUpdating">
            <Columns>
                <asp:BoundField DataField="email" HeaderText="email" SortExpression="email" />
            </Columns>
        </asp:GridView>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
            SelectCommand="SELECT [email] FROM [vw_Email]"
            DeleteCommand="sproc_DeleteEmail" DeleteCommandType="StoredProcedure"
            UpdateCommand="sproc_UpdateEmail" UpdateCommandType="StoredProcedure"
            >
            <DeleteParameters><asp:Parameter Name="email" Type="String" /></DeleteParameters>
            <UpdateParameters>
                <asp:Parameter Name="email" Type="String" />
                <asp:Parameter Name="newEmail" Type="String" />
            </UpdateParameters>
            </asp:SqlDataSource>

Now the code behind.

    protected void gvEmail_RowDeleting(object sender, GridViewDeleteEventArgs e) //DELETE
    {
        SqlConnection conn = new SqlConnection(SqlDataSource1.ConnectionString);
        System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand("sproc_DeleteEmail", conn);
        command.CommandType = System.Data.CommandType.StoredProcedure;
        conn.Open();
        string email = string.Empty;
        DataControlFieldCell cell = gvEmail.Rows[e.RowIndex].Cells[1] as DataControlFieldCell;
        gvEmail.Columns[0].ExtractValuesFromCell(
            e.Keys,
            cell,
            DataControlRowState.Normal,
            true);
        email = e.Keys[0].ToString();
        if (!string.IsNullOrEmpty(email))
        {
            command.Parameters.AddWithValue("@email", email);
            command.ExecuteNonQuery();
        }
        command.Parameters.Clear();
        conn.Close();
    }
    protected void gvEmail_OnRowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        SqlConnection conn = new SqlConnection(SqlDataSource1.ConnectionString);
        System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand("sproc_UpdateEmail", conn);
        command.CommandType = System.Data.CommandType.StoredProcedure;
        conn.Open();
        string newEmail = e.NewValues[0] as string;
        string email = e.OldValues[0] as string;
        if (!string.IsNullOrEmpty(email))
        {
            command.Parameters.AddWithValue("@email", email);
            command.Parameters.AddWithValue("@newEmail", newEmail);
            command.ExecuteNonQuery();
        }
        command.Parameters.Clear();
        conn.Close();
    }   

Note: Exception handling left off for brevity.
Reference: http://www.developerfusion.co.uk/show/91/7/

Using XML and XPath for a GridView

This demonstrates how to use XML and XPath with a GridView to display links:

    <asp:GridView ID="gvLinks" runat="server" DataSourceID="XmlDataSource1" AutoGenerateColumns="False">
    <Columns>
        <asp:TemplateField HeaderText="Link">
            <ItemTemplate>    
            <asp:HyperLink ID="HyperLink1" runat="server" Target="_blank" NavigateUrl='<%#XPath("href") %>'>
                <%#XPath("title")%>
            </asp:HyperLink>
            </ItemTemplate>    
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Description">
            <ItemTemplate>
                <asp:Label ID="lblrOwner" runat="server" Text=&lt;%#XPath("description")%&gt;></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
    </asp:GridView>
    <asp:XmlDataSource ID="XmlDataSource1" runat="server" DataFile="~/App_Data/Links.xml"
        XPath="links/link"></asp:XmlDataSource>

Here is the XML file:

<?xml version="1.0" encoding="utf-8" ?>
<links>
  <link>
    <title>Yahoo</title>
    <href>http://www.yahoo.com/</href>
    <owner>Yang</owner>
    <description>Yahoo web portal</description>
  </link>
  <link>
    <title>MSN</title>
    <href>http://www.msn.com/</href>
    <owner>Balmer</owner>
    <description>Microsoft web portal</description>
  </link>
  <link>
    <title>Delicious</title>
    <href>http://del.icio.us/</href>
    <owner></owner>
    <description>Internet bookmark manager</description>
  </link>
  <link>
    <title>YouTube</title>
    <href>http://youtube.com/</href>
    <owner></owner>
    <description>Internet videos</description>
  </link>
  <link>
    <title>SlashDot</title>
    <href>http://slashdot.org/</href>
    <owner></owner>
    <description>News that matters</description>
  </link>  
  
</links>

Reference: http://bytes.com/forum/thread528704.html

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