C＃將空行添加到GridView

Question

我遇到的小問題我的代碼無法修復。我有一個帶有ImageButton的GridView，它應該添加一個新的空行。出於某種原因，我得到這個錯誤：

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

所以這是在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> 

這是C＃代碼如何我試圖做到這一點：

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(); 
    } 
} 

感謝您的任何建議！

編輯

我現在明白了，我的數據表是空的，這樣是不行的，但我怎麼能得到GridView控件DataSet，並帶回了新的空行？我試着像這樣用同樣的錯誤：

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; 
    } 

的錯誤，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

嘗試過這樣的：

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; 
    } 

錯誤，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

其他建議？

SOLUTION

我做到了，我明白了做這樣的：

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

你的數據源是空的，這是爲什麼你的數據錶轉換成空對象，而異常扔

Answer 2

您的代碼僅適用於空gridview。因爲你不增加行索引。

對於添加新行gridview有一些關注。

您以前是否在gridview有datasource？如果您之前有一些datasource，然後您需要將datasource保存在viewstate中，並且在添加新行之前，您需要先提取gridview中的先前數據，然後添加一個新行。

按照下面的代碼

***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(); 
} 

首先設置初始行保存datasource ***設置在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(); 
} 

***組先前數據

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++; 
      } 
     } 
    } 
} 

***請點擊鏈接

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

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