从数据表中删除行给出错误表没有主键 [英] Remove row from datatable gives error table does not have primary key

问题描述

我有一个数据表，当我从中删除行时，它会抛出一个表没有主键的错误。

任何人都有解决方案吗？



i想要从数据表中删除选定的组合项目。



我尝试过的方法：

I have a datatable, when i remove row from it, it will throws an error that table does not have primary key.
any one have solution for it?

i want to remove selected item of combobox from the datatable.

What I have tried:

private void dropDownDemo_Load(object sender, EventArgs e)
       {

           dt.Columns.Add("Data");
           dt.Rows.Add("None");
           dt.Rows.Add("1st");
           dt.Rows.Add("2nd");
           dt.Rows.Add("3rd");
       }

public void removeSelected(string selected)
        {
            if (selected != "None")
            {
                foreach (DataRow row in dt.Rows)
                {
                    if (dt.Rows.Contains(selected))    //throw error here :- System.Data.MissingPrimaryKeyException: Table doesn't have a primary key.
                    {
                        dt.Rows.Remove(row);
                    }
                }
            }
        }

推荐答案

下面是删除行的代码。

Hi,

Below, code to delete rows.

public void removeSelected(string selected)
        {
            try
            {
                if (selected != "None")
                {
                    DataRow[] drs = dt.Select("Data = '" + selected + "'");

                    if (drs.Length > 0)
                    {
                        foreach (DataRow dr in drs)
                        {
                            dr.Delete();
                            dt.AcceptChanges();
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                this.lblError.Text = ex.Message; 
            }
        }

用下面的循环替换你的foreach循环来识别特定的行然后删除它应该可以解决问题。



for（int i = dt.Rows.Count-1; i> = 0; i--）

{

DataRow dr = dt.Rows [i];

if（dr [Data] ==（（ComboBox）sender）.Text）

dr.Delete（）;

}

Replacing your foreach loop with the below loop to identify the specific row and then delete it should do the trick.

for(int i = dt.Rows.Count-1; i >= 0; i--)
{
DataRow dr = dt.Rows[i];
if (dr["Data"] == ((ComboBox)sender).Text)
dr.Delete();
}

通过主键识别和比较行。你问的是这组行是否包含一行主键选择。



另外，你永远不应该在迭代中对迭代器进行更改。这也会引发错误。



试试这个：

The rows are identified and compared via a primary key. You're asking if the set of rows contains a row with the primary key selected.

Also, you should never make changes to an iterator within the iteration. This will throw an error also.

Try this instead:

private void dropDownDemo_Load(object sender, EventArgs e)
        {
 
            dt.Columns.Add("Data");
            dt.Rows.Add("None");
            dt.Rows.Add("1st");
            dt.Rows.Add("2nd");
            dt.Rows.Add("3rd");
        }
public void removeSelected(string selected)
        {
            var dtTemp = new DataTable;
            dtTemp .Columns.Add("Data");
            if (selected != "None")
            {
                foreach (DataRow row in dt.Rows)
                {
                    if (!dt.Rows["Data"].Contains(selected))   
                    {
                        dtTemp.Rows.Add(row)
                    }
                }
            }
            dt = dtTemp;
        }

另一种方法是添加 Break; 删除行后，但这很干净

Another way would be to add a Break; after you remove the row, but this is pretty clean

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