Newbie -- what are these errors -- System.NullReferenceException

I am new to .NET and C#. I am deploying the SPS web part that appears below
and I am getting System.NullReferenceException in my CreateChildControls
method. The last item shown by my debugger prior to the exception is
"Setting ID."
Any assistance would be greatly appreciated.
Joe Mack
CODE
--
using System;
using System.ComponentModel;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml.Serialization;
using System.Runtime.InteropServices;
using System.Diagnostics;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Utilities;
using Microsoft.SharePoint.WebPartPages;
using Microsoft.SharePoint.WebPartPages.Communication;
using System.Data;
namespace adSearch
{
/// <summary>
/// Description for WebPart1.
/// </summary>
[DefaultProperty("Text"),
ToolboxData("<{0}:adSearchWP runat=server></{0}:adSearchWP>"),
XmlRoot(Namespace="adSearch")]
public class adSearchWP : Microsoft.SharePoint.WebPartPages.WebPart,
Microsoft.SharePoint.WebPartPages.Communication.IRowProvider
{
public event RowProviderInitEventHandler RowProviderInit;
public event RowReadyEventHandler RowReady;
private bool isConnected = false;
private bool submitClicked = false;
private string[] myFieldNames;
private string[] myFieldDisplayNames;
private DataGrid myDataGrid;
// Create Web Part user interface controls.
protected TextBox searchBox;
protected Button searchButton;
public override void EnsureInterfaces()
{
Debug.Write("Ensuring interfaces.");
RegisterInterface("MGRowProvider", //InterfaceName
InterfaceTypes.IRowProvider, //InterfaceType
WebPart.UnlimitedConnections, //MaxConnections
ConnectionRunAt.Server, //RunAtOptions
this, //InterfaceObject
"",
//InterfaceClientReference
"Provide Data To...", //MenuLabel
"Provides a row of data to a consumer Web Part.", //Description
true);
//allowCrossPageConnection
}
public override ConnectionRunAt CanRunAt()
{
return ConnectionRunAt.Server;
}
public override void PartCommunicationConnect(
string interfaceName,
WebPart connectedPart,
string connectedInterfaceName,
ConnectionRunAt runAt)
{
if (interfaceName == "MGRowProvider")
{
Debug.Write("Connected.");
isConnected = true;
EnsureChildControls();
}
}
public override void PartCommunicationInit()
{
if( isConnected)
{
if (RowProviderInit != null)
{
RowProviderInitEventArgs rowProviderInitArgs = new
RowProviderInitEventArgs();
rowProviderInitArgs.FieldList = myFieldNames;
rowProviderInitArgs.FieldDisplayList = myFieldDisplayNames;
RowProviderInit(this,rowProviderInitArgs
);
}
}
else
Debug.Write("Need to send something...init");
}
public override void PartCommunicationMain()
{
if (isConnected)
{
if (RowReady != null)
{
RowReadyEventArgs rowReadyArgs = new RowReadyEventArgs();
if (submitClicked)
{
DataRow[] dr = new DataRow[1];
dr[0] = ((DataTable)myDataGrid.DataSource).Rows[0];
rowReadyArgs.Rows = dr;
rowReadyArgs.SelectionStatus = "Standard";
}
RowReady(this,rowReadyArgs);
}
}
else
Debug.Write("Need to send something...main");
}
public override InitEventArgs GetInitEventArgs(string interfaceName)
{
if (interfaceName == "MGRowProvider")
{
EnsureChildControls();
RowProviderInitEventArgs rowProviderInitArgs = new
RowProviderInitEventArgs();
rowProviderInitArgs.FieldList = myFieldNames;
rowProviderInitArgs.FieldDisplayList = myFieldDisplayNames;
return(rowProviderInitArgs);
}
else
return(null);
}
/// <summary>
/// Render this Web Part to the output parameter specified.
/// </summary>
/// <param name="output"> The HTML writer to write out to </param>
protected override void RenderWebPart(HtmlTextWriter output)
{
EnsureChildControls();
Debug.Write("rendering web part.");
output.RenderBeginTag("div");
// Check if connected.
if(isConnected)
{
Debug.Write("Connected. Rendering web part");
// Line break.
output.RenderBeginTag(HtmlTextWriterTag.Br);
output.RenderEndTag();
output.RenderBeginTag(HtmlTextWriterTag.Table);
output.RenderBeginTag(HtmlTextWriterTag.Tr);
output.RenderBeginTag(HtmlTextWriterTag.Th);
output.Write("Search For:");
output.RenderEndTag();
output.RenderBeginTag("td");
searchBox.RenderControl(output);
output.RenderEndTag();
output.RenderBeginTag("td");
searchButton.RenderControl(output);
output.RenderEndTag();
output.RenderEndTag();
output.RenderEndTag();
}
else
{
Debug.Write("Not connected, writing message.");
// The Web Part isn't connected.
output.Write("Not connected.");
}
output.RenderEndTag();
}
protected override void CreateChildControls()
{
Debug.Write("Creating child controls");
try
{
Debug.Write("Setting ID.");
searchBox.ID = "srchBox";
Debug.Write("Done setting ID. Setting width.");
this.searchBox.Width=Unit.Percentage(100);
Debug.Write("Done setting width. Adding search box.");
this.Controls.Add(searchBox);
Debug.Write("Created Search Box");
}
catch (Exception ex)
{
Debug.Write("Exception - search box: " + ex);
}
try
{
this.searchButton.Text = "Submit";
this.searchButton.Click += new System.EventHandler(searchButton_Click);
this.Controls.Add(searchButton);
Debug.Write("Created Search Button");
}
catch (Exception ex)
{
Debug.Write("Exception - search button: " + ex);
}
}
private void searchButton_Click(object sender, EventArgs e)
{
submitClicked = true; //user clicked button, set to true
Debug.Write("Button clicked.");
DataTable dataTable = new DataTable();
// Add three column objects to the table.
DataColumn anrColumn = new DataColumn();
anrColumn.DataType = System.Type.GetType("System.String");
anrColumn.ColumnName = "anr";
anrColumn.Caption = "ANR";
dataTable.Columns.Add(anrColumn);
DataRow dataRow;
dataRow = dataTable.NewRow();
// Then add the new row to the collection.
dataRow["anr"] = searchBox.Text;
dataTable.Rows.Add(dataRow);
myDataGrid.DataSource = dataTable;
myDataGrid.ID = "DataGrid";
myDataGrid.Attributes.Add("WDFLibID", "ServerSideRowProvider_DataGrid");
myDataGrid.DataBind();
//Set the DataTable FieldName information.
//This information will be passed to the Consumer by
//firing the RowProviderInit event.
int columnCount = dataTable.Columns.Count;
myFieldNames = new string[columnCount];
myFieldDisplayNames = new string[columnCount];
for(int i = 0; i < columnCount; i++)
{
myFieldNames[i] = dataTable.Columns[i].ColumnName;
myFieldDisplayNames[i] = dataTable.Columns[i].Caption;
}
}
}
}System.NullReferenceException iundicates that you are, in your code
somewhere, referencing an object that doesn't exist. For example:
object o;
string s = o.ToString(); // As o is not initialized to anything, you will
get a System.NullReferenceException
HTH,
Kevin Spencer
.Net Developer
Microsoft MVP
Neither a follower
nor a lender be.
"Joe" <Joe@.discussions.microsoft.com> wrote in message
news:F9BD4158-B270-44D2-8572-379F055F4F4C@.microsoft.com...
> I am new to .NET and C#. I am deploying the SPS web part that appears
below
> and I am getting System.NullReferenceException in my CreateChildControls
> method. The last item shown by my debugger prior to the exception is
> "Setting ID."
> Any assistance would be greatly appreciated.
> Joe Mack
> --
> CODE
> --
> using System;
> using System.ComponentModel;
> using System.Web.UI;
> using System.Web.UI.WebControls;
> using System.Xml.Serialization;
> using System.Runtime.InteropServices;
> using System.Diagnostics;
> using Microsoft.SharePoint;
> using Microsoft.SharePoint.Utilities;
> using Microsoft.SharePoint.WebPartPages;
> using Microsoft.SharePoint.WebPartPages.Communication;
> using System.Data;
> namespace adSearch
> {
> /// <summary>
> /// Description for WebPart1.
> /// </summary>
> [DefaultProperty("Text"),
> ToolboxData("<{0}:adSearchWP runat=server></{0}:adSearchWP>"),
> XmlRoot(Namespace="adSearch")]
> public class adSearchWP : Microsoft.SharePoint.WebPartPages.WebPart,
> Microsoft.SharePoint.WebPartPages.Communication.IRowProvider
> {
> public event RowProviderInitEventHandler RowProviderInit;
> public event RowReadyEventHandler RowReady;
> private bool isConnected = false;
> private bool submitClicked = false;
> private string[] myFieldNames;
> private string[] myFieldDisplayNames;
> private DataGrid myDataGrid;
>
> // Create Web Part user interface controls.
> protected TextBox searchBox;
> protected Button searchButton;
> public override void EnsureInterfaces()
> {
> Debug.Write("Ensuring interfaces.");
> RegisterInterface("MGRowProvider", //InterfaceName
> InterfaceTypes.IRowProvider, //InterfaceType
> WebPart.UnlimitedConnections, //MaxConnections
> ConnectionRunAt.Server, //RunAtOptions
> this, //InterfaceObject
> "",
> //InterfaceClientReference
> "Provide Data To...", //MenuLabel
> "Provides a row of data to a consumer Web Part.", //Description
> true);
> //allowCrossPageConnection
> }
> public override ConnectionRunAt CanRunAt()
> {
> return ConnectionRunAt.Server;
> }
> public override void PartCommunicationConnect(
> string interfaceName,
> WebPart connectedPart,
> string connectedInterfaceName,
> ConnectionRunAt runAt)
> {
> if (interfaceName == "MGRowProvider")
> {
> Debug.Write("Connected.");
> isConnected = true;
> EnsureChildControls();
> }
> }
> public override void PartCommunicationInit()
> {
> if( isConnected)
> {
> if (RowProviderInit != null)
> {
> RowProviderInitEventArgs rowProviderInitArgs = new
> RowProviderInitEventArgs();
> rowProviderInitArgs.FieldList = myFieldNames;
> rowProviderInitArgs.FieldDisplayList = myFieldDisplayNames;
> RowProviderInit(this,rowProviderInitArgs
);
> }
> }
> else
> Debug.Write("Need to send something...init");
> }
> public override void PartCommunicationMain()
> {
> if (isConnected)
> {
> if (RowReady != null)
> {
> RowReadyEventArgs rowReadyArgs = new RowReadyEventArgs();
> if (submitClicked)
> {
> DataRow[] dr = new DataRow[1];
> dr[0] = ((DataTable)myDataGrid.DataSource).Rows[0];
> rowReadyArgs.Rows = dr;
> rowReadyArgs.SelectionStatus = "Standard";
> }
> RowReady(this,rowReadyArgs);
> }
> }
> else
> Debug.Write("Need to send something...main");
> }
> public override InitEventArgs GetInitEventArgs(string interfaceName)
> {
> if (interfaceName == "MGRowProvider")
> {
> EnsureChildControls();
> RowProviderInitEventArgs rowProviderInitArgs = new
> RowProviderInitEventArgs();
> rowProviderInitArgs.FieldList = myFieldNames;
> rowProviderInitArgs.FieldDisplayList = myFieldDisplayNames;
> return(rowProviderInitArgs);
> }
> else
> return(null);
> }
> /// <summary>
> /// Render this Web Part to the output parameter specified.
> /// </summary>
> /// <param name="output"> The HTML writer to write out to </param>
> protected override void RenderWebPart(HtmlTextWriter output)
> {
> EnsureChildControls();
> Debug.Write("rendering web part.");
> output.RenderBeginTag("div");
> // Check if connected.
> if(isConnected)
> {
> Debug.Write("Connected. Rendering web part");
> // Line break.
> output.RenderBeginTag(HtmlTextWriterTag.Br);
> output.RenderEndTag();
> output.RenderBeginTag(HtmlTextWriterTag.Table);
> output.RenderBeginTag(HtmlTextWriterTag.Tr);
> output.RenderBeginTag(HtmlTextWriterTag.Th);
> output.Write("Search For:");
> output.RenderEndTag();
> output.RenderBeginTag("td");
> searchBox.RenderControl(output);
> output.RenderEndTag();
> output.RenderBeginTag("td");
> searchButton.RenderControl(output);
> output.RenderEndTag();
> output.RenderEndTag();
> output.RenderEndTag();
> }
> else
> {
> Debug.Write("Not connected, writing message.");
> // The Web Part isn't connected.
> output.Write("Not connected.");
> }
> output.RenderEndTag();
> }
> protected override void CreateChildControls()
> {
> Debug.Write("Creating child controls");
> try
> {
> Debug.Write("Setting ID.");
> searchBox.ID = "srchBox";
> Debug.Write("Done setting ID. Setting width.");
> this.searchBox.Width=Unit.Percentage(100);
> Debug.Write("Done setting width. Adding search box.");
> this.Controls.Add(searchBox);
> Debug.Write("Created Search Box");
> }
> catch (Exception ex)
> {
> Debug.Write("Exception - search box: " + ex);
> }
> try
> {
> this.searchButton.Text = "Submit";
> this.searchButton.Click += new System.EventHandler(searchButton_Click);
> this.Controls.Add(searchButton);
> Debug.Write("Created Search Button");
> }
> catch (Exception ex)
> {
> Debug.Write("Exception - search button: " + ex);
> }
> }
> private void searchButton_Click(object sender, EventArgs e)
> {
> submitClicked = true; //user clicked button, set to true
> Debug.Write("Button clicked.");
> DataTable dataTable = new DataTable();
> // Add three column objects to the table.
> DataColumn anrColumn = new DataColumn();
> anrColumn.DataType = System.Type.GetType("System.String");
> anrColumn.ColumnName = "anr";
> anrColumn.Caption = "ANR";
> dataTable.Columns.Add(anrColumn);
> DataRow dataRow;
> dataRow = dataTable.NewRow();
> // Then add the new row to the collection.
> dataRow["anr"] = searchBox.Text;
> dataTable.Rows.Add(dataRow);
> myDataGrid.DataSource = dataTable;
> myDataGrid.ID = "DataGrid";
> myDataGrid.Attributes.Add("WDFLibID", "ServerSideRowProvider_DataGrid");
> myDataGrid.DataBind();
> //Set the DataTable FieldName information.
> //This information will be passed to the Consumer by
> //firing the RowProviderInit event.
> int columnCount = dataTable.Columns.Count;
> myFieldNames = new string[columnCount];
> myFieldDisplayNames = new string[columnCount];
> for(int i = 0; i < columnCount; i++)
> {
> myFieldNames[i] = dataTable.Columns[i].ColumnName;
> myFieldDisplayNames[i] = dataTable.Columns[i].Caption;
> }
> }
> }
> }
>
>
On Tue, 9 Nov 2004 10:53:03 -0800, Joe <Joe@.discussions.microsoft.com>
wrote:

>I am new to .NET and C#. I am deploying the SPS web part that appears belo
w
>and I am getting System.NullReferenceException in my CreateChildControls
>method. The last item shown by my debugger prior to the exception is
>"Setting ID."
>Any assistance would be greatly appreciated.
>Joe Mack
> <SNIP CODE>
You are not instantiating search Box before assigning the .ID in this
line:
searchBox.ID = "srchBox";
You need to instantiate the control like so:
searchBox = new TextBox();
This also goes for any other controls you use as well.
Thanks,
Chris Simmons
newsgroup.replies@.netchris.com