C＃将空行添加到GridView

Question

我遇到的小问题我的代码无法修复。我有一个带有ImageButton的GridView，它应该添加一个新的空行。出于某种原因，我得到这个错误：

Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.] CTI_DFC.Default.gv_Steps_RowCommand(Object sender, GridViewCommandEventArgs e) +469
System.Web.UI.WebControls.GridView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +172
System.Web.UI.WebControls.GridViewRow.OnBubbleEvent(Object source, EventArgs e) +163 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +83
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3771

所以这是在GridView我：

<asp:GridView ID="gv_Steps" runat="server" CssClass="lbl_user" Font-Names="Verdana" Font-Size="10px" HeaderStyle-Height="23.5px" HorizontalAlign="Center" 
    RowStyle-Height="23.5px" ShowHeaderWhenEmpty="True" style="z-index: 1; left: 8px; top: 143px; position: absolute; height: 20px; width: 1178px;" AutoGenerateColumns="False" OnRowCommand="gv_Steps_RowCommand"> 
    <AlternatingRowStyle BackColor="#DCE4FF" /> 
    <Columns> 
     <asp:TemplateField HeaderText="Step" HeaderStyle-HorizontalAlign="Left" > 
      <ItemTemplate> 
       <asp:TextBox ID="txt_Step" HeaderStyle-HorizontalAlign="Left" runat="server" Width="150px" Text='<%# Bind("Step") %>'/> 
      </ItemTemplate> 
     </asp:TemplateField> 
     <asp:TemplateField HeaderText="Server" HeaderStyle-HorizontalAlign="Left" > 
      <ItemTemplate> 
       <asp:TextBox ID="txt_Server" HeaderStyle-HorizontalAlign="Left" runat="server" Width="150px" Text='<%# Bind("Server") %>'/> 
      </ItemTemplate> 
     </asp:TemplateField> 
     <asp:TemplateField HeaderText="Type" HeaderStyle-HorizontalAlign="Left" > 
      <ItemTemplate> 
       <asp:TextBox ID="txt_Type" HeaderStyle-HorizontalAlign="Left" runat="server" Width="150px" Text='<%# Bind("Type") %>'/> 
      </ItemTemplate> 
     </asp:TemplateField> 
     <asp:TemplateField HeaderText="Job" HeaderStyle-HorizontalAlign="Left" > 
      <ItemTemplate> 
       <asp:TextBox ID="txt_Job" HeaderStyle-HorizontalAlign="Left" runat="server" Width="150px" Text='<%# Bind("Job") %>'/> 
      </ItemTemplate> 
     </asp:TemplateField> 
     <asp:TemplateField HeaderText="Number" HeaderStyle-HorizontalAlign="Left" > 
      <ItemTemplate> 
       <asp:TextBox ID="txt_Number" HeaderStyle-HorizontalAlign="Left" runat="server" Width="150px" Text='<%# Bind("Number") %>'/> 
      </ItemTemplate> 
     </asp:TemplateField> 
     <asp:TemplateField HeaderText="" ItemStyle-Width="15px" ItemStyle-Wrap="false"> 
      <ItemTemplate> 
       <asp:ImageButton ID="btn_AddRow" runat="server" AlternateText="Add Row" CommandArgument="<%# Container.DataItemIndex %>" CommandName="Add" ImageUrl="./Img/ADD.png" ToolTip="Add Row without Change" /> 
      </ItemTemplate> 
     </asp:TemplateField> 
     <asp:TemplateField HeaderText="" ItemStyle-Width="15px" ItemStyle-Wrap="false"> 
      <ItemTemplate> 
       <asp:ImageButton ID="btn_DeleteRow" runat="server" AlternateText="Delete Row" CommandArgument="<%# Container.DataItemIndex %>" CommandName="Delete" ImageUrl="./Img/DEL.png" ToolTip="Delete Row without Change" /> 
      </ItemTemplate> 
     </asp:TemplateField> 
    </Columns> 
    <HeaderStyle BackColor="#0B4DA2" Font-Bold="True" ForeColor="White" /> 
    <RowStyle Height="23px" /> 
</asp:GridView> 

这是C＃代码如何我试图做到这一点：

protected void gv_Steps_RowCommand(object sender, GridViewCommandEventArgs e) 
{ 
    int intIndex = Convert.ToInt32(e.CommandArgument); //will be used for Delete 

    if (e.CommandName == "Delete" && (gv_Steps.Rows.Count > 1)) 
    { 
     //Nothing done yet 
    } 
    if (e.CommandName == "Add") 
    { 
     DataTable dt = gv_Steps.DataSource as DataTable; 
     DataRow dr = dt.NewRow(); 
     dt.Rows.Add(dr); 

     gv_Steps.DataSource = dt; 
     gv_Steps.DataBind(); 
    } 
} 

感谢您的任何建议！

编辑

我现在明白了，我的数据表是空的，这样是不行的，但我怎么能得到GridView控件DataSet，并带回了新的空行？我试着像这样用同样的错误：

protected void gv_Steps_RowCommand(object sender, GridViewCommandEventArgs e) 
    { 
     int intIndex = Convert.ToInt32(e.CommandArgument); //will be used for Delete 

     if (e.CommandName == "Delete" && (gv_Steps.Rows.Count > 1)) 
     { 
      //Nothing done yet 
     } 
     if (e.CommandName == "Add") 
     { 
      DataTable dt = GridviewToDataTable(); 
      DataRow dr = dt.NewRow(); 
      dt.Rows.Add(dr); 

      gv_Steps.DataSource = dt; 
      gv_Steps.DataBind(); 
     } 
    } 

private DataTable GridviewToDataTable() 
    { 
     DataTable dt = new DataTable(); 
     dt.Columns.Add(new DataColumn("Step", typeof(string))); 
     dt.Columns.Add(new DataColumn("Server", typeof(string))); 
     dt.Columns.Add(new DataColumn("Type", typeof(string))); 
     dt.Columns.Add(new DataColumn("Job", typeof(string))); 
     dt.Columns.Add(new DataColumn("Number", typeof(string))); 

     foreach (GridViewRow row in gv_Steps.Rows) 
     { 
      dt.Rows.Add(); 
      dt.Rows[row.RowIndex][0] = ((TextBox)row.FindControl("Step")).Text; 
      dt.Rows[row.RowIndex][1] = ((TextBox)row.FindControl("Server")).Text; 
      dt.Rows[row.RowIndex][2] = ((TextBox)row.FindControl("Type")).Text; 
      dt.Rows[row.RowIndex][3] = ((TextBox)row.FindControl("Job")).Text; 
      dt.Rows[row.RowIndex][4] = ((TextBox)row.FindControl("Number")).Text; 
     } 

     return dt; 
    } 

的错误，我得到：

Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.] CTI_DFC.Default.GridviewToDataTable() +1161
CTI_DFC.Default.gv_Steps_RowCommand(Object sender, GridViewCommandEventArgs e) +392
System.Web.UI.WebControls.GridView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +172
System.Web.UI.WebControls.GridViewRow.OnBubbleEvent(Object source, EventArgs e) +163 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +83
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3771

EDIT 2

尝试过这样的：

protected void gv_Steps_RowCommand(object sender, GridViewCommandEventArgs e) 
    { 
     int intIndex = Convert.ToInt32(e.CommandArgument); //will be used for Delete 

     if (e.CommandName == "Delete" && (gv_Steps.Rows.Count > 1)) 
     { 
      //Nothing done yet 
     } 
     if (e.CommandName == "Add") 
     { 
      DataTable dt = GridviewToDataTable(gv_Steps); 
      DataRow dr = dt.NewRow(); 
      dt.Rows.Add(dr); 

      gv_Steps.DataSource = dt; 
      gv_Steps.DataBind(); 
      GridviewToDataTable(gv_Steps); 
     } 
    } 
private DataTable GridviewToDataTable(GridView gv) 
    { 
     DataTable dt = new DataTable(); 
     dt.Columns.Add(new DataColumn("Step", typeof(string))); 
     dt.Columns.Add(new DataColumn("Server", typeof(string))); 
     dt.Columns.Add(new DataColumn("Type", typeof(string))); 
     dt.Columns.Add(new DataColumn("Job", typeof(string))); 
     dt.Columns.Add(new DataColumn("Number", typeof(string))); 
     foreach (GridViewRow row in gv.Rows) 
     { 
      dt.Rows.Add(); 
      dt.Rows[row.RowIndex][0] = ((TextBox)row.FindControl("Step")).Text; 
      dt.Rows[row.RowIndex][1] = ((TextBox)row.FindControl("Server")).Text; 
      dt.Rows[row.RowIndex][2] = ((TextBox)row.FindControl("Type")).Text; 
      dt.Rows[row.RowIndex][3] = ((TextBox)row.FindControl("Job")).Text; 
      dt.Rows[row.RowIndex][4] = ((TextBox)row.FindControl("Number")).Text; 
     } 
     gv.DataSource = dt; 
     gv.DataBind(); 
     return dt; 
    } 

错误，我得到：

Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.] CTI_DFC.Default.GridviewToDataTable(GridView gv) +1145
CTI_DFC.Default.gv_Steps_RowCommand(Object sender, GridViewCommandEventArgs e) +407
System.Web.UI.WebControls.GridView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +172
System.Web.UI.WebControls.GridViewRow.OnBubbleEvent(Object source, EventArgs e) +163 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +83
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3771

其他建议？

SOLUTION

我做到了，我明白了做这样的：

private DataTable GridviewToDataTable(GridView gv) 
    { 
     DataTable dt = new DataTable(); 
     dt.Columns.Add(new DataColumn("Step", typeof(string))); 
     dt.Columns.Add(new DataColumn("Server", typeof(string))); 
     dt.Columns.Add(new DataColumn("Type", typeof(string))); 
     dt.Columns.Add(new DataColumn("Job", typeof(string))); 
     dt.Columns.Add(new DataColumn("Number", typeof(string))); 
     foreach (GridViewRow row in gv.Rows) 
     { 
      dt.Rows.Add(); 
      dt.Rows[row.RowIndex][0] = (row.FindControl("txt_Step") as TextBox).Text; 
      dt.Rows[row.RowIndex][1] = (row.FindControl("txt_Server") as TextBox).Text; 
      dt.Rows[row.RowIndex][2] = (row.FindControl("txt_Type") as TextBox).Text; 
      dt.Rows[row.RowIndex][3] = (row.FindControl("txt_Job") as TextBox).Text; 
      dt.Rows[row.RowIndex][4] = (row.FindControl("txt_Number") as TextBox).Text; 
     } 
     lbl_Fehlermeldung.Text = dt.Rows[0][0].ToString(); 
     lbl_Fehlermeldung.Visible = true; 
     gv.DataSource = dt; 
     gv.DataBind(); 
     return dt; 
    } 

Answer 1

你的数据源是空的，这是为什么你的数据表转换成空对象，而异常扔

Answer 2

您的代码仅适用于空gridview。因为你不增加行索引。

对于添加新行gridview有一些关注。

您以前是否在gridview有datasource？如果您之前有一些datasource，然后您需要将datasource保存在viewstate中，并且在添加新行之前，您需要先提取gridview中的先前数据，然后添加一个新行。

按照下面的代码

***在viewstate

private void SetInitialRow() 
{ 
    DataTable dt = new DataTable(); 
    DataRow dr = null; 
    dt.Columns.Add(new DataColumn("RowNumber", typeof(string))); 
    dt.Columns.Add(new DataColumn("Column1", typeof(string))); 
    dt.Columns.Add(new DataColumn("Column2", typeof(string))); 
    dt.Columns.Add(new DataColumn("Column3", typeof(string))); 
    dr = dt.NewRow(); 
    dr["RowNumber"] = 1; 
    dr["Column1"] = string.Empty; 
    dr["Column2"] = string.Empty; 
    dr["Column3"] = string.Empty; 
    dt.Rows.Add(dr); 
    //dr = dt.NewRow(); 

    //Store the DataTable in ViewState 
    ViewState["CurrentTable"] = dt; 

    Gridview1.DataSource = dt; 
    Gridview1.DataBind(); 
} 

首先设置初始行保存datasource ***设置在page_load

protected void Page_Load(object sender, EventArgs e) 
{ 
    if (!Page.IsPostBack) 
    { 
     SetInitialRow(); 
    } 
} 

***添加新行gridview

private void AddNewRowToGrid() 
{ 
    int rowIndex = 0; 

    if (ViewState["CurrentTable"] != null) 
    { 
     DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"]; 
     DataRow drCurrentRow = null; 
     if (dtCurrentTable.Rows.Count > 0) 
     { 
      for (int i = 1; i <= dtCurrentTable.Rows.Count; i++) 
      { 
       //extract the TextBox values 
       TextBox box1 = (TextBox)Gridview1.Rows[rowIndex].Cells[1].FindControl("TextBox1"); 
       TextBox box2 = (TextBox)Gridview1.Rows[rowIndex].Cells[2].FindControl("TextBox2"); 
       TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].Cells[3].FindControl("TextBox3"); 

       drCurrentRow = dtCurrentTable.NewRow(); 
       drCurrentRow["RowNumber"] = i + 1; 

       dtCurrentTable.Rows[i - 1]["Column1"] = box1.Text; 
       dtCurrentTable.Rows[i - 1]["Column2"] = box2.Text; 
       dtCurrentTable.Rows[i - 1]["Column3"] = box3.Text; 

       rowIndex++; 
      } 
      dtCurrentTable.Rows.Add(drCurrentRow); 
      ViewState["CurrentTable"] = dtCurrentTable; 

      Gridview1.DataSource = dtCurrentTable; 
      Gridview1.DataBind(); 
     } 
    } 
    else 
    { 
     Response.Write("ViewState is null"); 
    } 

    //Set Previous Data on Postbacks 
    SetPreviousData(); 
} 

***组先前数据

private void SetPreviousData() 
{ 
    int rowIndex = 0; 
    if (ViewState["CurrentTable"] != null) 
    { 
     DataTable dt = (DataTable)ViewState["CurrentTable"]; 
     if (dt.Rows.Count > 0) 
     { 
      for (int i = 0; i < dt.Rows.Count; i++) 
      { 
       TextBox box1 = (TextBox)Gridview1.Rows[rowIndex].Cells[1].FindControl("TextBox1"); 
       TextBox box2 = (TextBox)Gridview1.Rows[rowIndex].Cells[2].FindControl("TextBox2"); 
       TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].Cells[3].FindControl("TextBox3"); 

       box1.Text = dt.Rows[i]["Column1"].ToString(); 
       box2.Text = dt.Rows[i]["Column2"].ToString(); 
       box3.Text = dt.Rows[i]["Column3"].ToString(); 

       rowIndex++; 
      } 
     } 
    } 
} 

***请点击链接

protected void ButtonAdd_Click(object sender, EventArgs e) 
    { 
     AddNewRowToGrid(); 
    } 

SORCE链接https://www.aspsnippets.com/Articles/Add-new-Row-to-GridView-on-Button-Click-in-ASPNet.aspx