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

G

Guest

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 = dataTable.Columns.ColumnName;
myFieldDisplayNames = dataTable.Columns.Caption;
}
}

}
}
 
K

Kevin Spencer

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 said:
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 = dataTable.Columns.ColumnName;
myFieldDisplayNames = dataTable.Columns.Caption;
}
}

}
}
Click to expand...
 
G

Guest

Kevin:

Thanks.

I was failing to instantiate my objects in the CreateChildControls method.
All I did was add two lines: "searchBox = new TextBox();" and
"searchButton = new Button();"

Joe


Kevin Spencer said:
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 said:
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 = dataTable.Columns.ColumnName;
myFieldDisplayNames = dataTable.Columns.Caption;
}
}

}
}
Click to expand...
Click to expand...
 
C

Chris Simmons

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

<SNIP CODE>
Click to expand...

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.
 

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