如何将新数据添加到数据网格中，同时保留以前存在的数据？

Question

我正在从 SQL 中选择数据到数据网格中，代码工作正常，但它正在从我的数据网格中删除以前的数据。

我的代码（C# WPF SQL 数据网格）：

  private void enter(object sender, KeyEventArgs e)
        {
            try
            {
                if (e.Key == Key.Enter)
                {
                    SqlConnection com = new SqlConnection("Server = localhost; database = PrimaSOFT ; integrated security = true");

                    SqlCommand cmd = new SqlCommand("produktit", com);
                    cmd.CommandType = System.Data.CommandType.StoredProcedure;
                    cmd.Parameters.AddWithValue("@Barkodi", txtBarkodi.Text);
                    //Created a new DataTable

                    SqlDataAdapter da = new SqlDataAdapter(cmd);



                    DataColumn dc = new DataColumn();//Made a new DataColumn to populate above DataTable
                    dc.DataType = System.Type.GetType("System.String");//Defined the DataType inside, this can be [[int]] if you want.
                    dc.ColumnName = "Barkodi";//Gave it a name (important for the custom expression - can only be one word so use underscores if you need multiple words)

                    DataColumn dc2 = new DataColumn();
                    dc2.DataType = System.Type.GetType("System.String");
                    dc2.ColumnName = "Emertimi";

                    DataColumn dc3 = new DataColumn();
                    dc3.DataType = System.Type.GetType("System.Decimal");
                    dc3.ColumnName = "Sasia";

                    DataColumn dc4 = new DataColumn();
                    dc4.DataType = System.Type.GetType("System.Decimal");
                    dc4.ColumnName = "Cmimi";

                    DataColumn dc5 = new DataColumn();
                    dc5.DataType = System.Type.GetType("System.String");
                    dc5.Caption = "sds";

                    dc5.ColumnName = "TVSH";

                    DataColumn dc6 = new DataColumn();
                    dc6.DataType = System.Type.GetType("System.String");
                    dc6.ColumnName = "Total";
                    dc6.Expression = "Cmimi * Sasia";//Multiplying the Price and Quantity DataColumns

                    dataTable.Columns.Add(dc);//Add them to the DataTable
                    dataTable.Columns.Add(dc2);
                    dataTable.Columns.Add(dc3);
                    dataTable.Columns.Add(dc4);
                    dataTable.Columns.Add(dc5);
                    dataTable.Columns.Add(dc6);

                    dtgartikujt.ItemsSource = dataTable.DefaultView;//Set the DataGrid ItemSource to this new generated DataTable

                    com.Open();//Open the SQL connection

                    SqlDataReader reader = cmd.ExecuteReader();//Create a SqlDataReader

                    while (reader.Read())//For each row that the SQL query returns do
                    {
                        DataRow dr = dataTable.NewRow();//Create new DataRow to populate the DataTable (which is currently binded to the DataGrid)
                        dr[0] = reader[0];//Fill DataTable column 0 current row (Product) with reader[0] (Product from sql)
                        dr[1] = reader[1];
                        dr[2] = reader[2];
                        dr[3] = reader[3];
                        dr[4] = reader[4];


                        dataTable.Rows.Add(dr);//Add the new created DataRow to the DataTable

                    }
                }
            }

求和码

                    object sumObject;
                    sumObject = dataTable.Compute("Sum(Totali)", 
                     string.Empty);
                    txttotali.Text = sumObject.ToString();

我希望在不删除以前数据的情况下在数据网格中显示新数据。 我应该如何处理？

已编辑：我还附上了求和代码，对数据网格列求和，并显示到文本框

Answer 1

我想我理解你在做什么：将 dataTable 代码与 Sql(ADO.NET) 代码分开，并且只运行一次 dataTable 部分。因此，例如在form_load 中运行CreateTable：

public void CreateTable()
{
 DataColumn dc = new DataColumn();//Made a new DataColumn to populate above DataTable
                    dc.DataType = System.Type.GetType("System.String");//Defined the DataType inside, this can be [[int]] if you want.
                    dc.ColumnName = "Barkodi";//Gave it a name (important for the custom expression - can only be one word so use underscores if you need multiple words)

                    DataColumn dc2 = new DataColumn();
                    dc2.DataType = System.Type.GetType("System.String");
                    dc2.ColumnName = "Emertimi";

                    DataColumn dc3 = new DataColumn();
                    dc3.DataType = System.Type.GetType("System.Decimal");
                    dc3.ColumnName = "Sasia";

                    DataColumn dc4 = new DataColumn();
                    dc4.DataType = System.Type.GetType("System.Decimal");
                    dc4.ColumnName = "Cmimi";

                    DataColumn dc5 = new DataColumn();
                    dc5.DataType = System.Type.GetType("System.String");
                    dc5.Caption = "sds";

                    dc5.ColumnName = "TVSH";

                    DataColumn dc6 = new DataColumn();
                    dc6.DataType = System.Type.GetType("System.String");
                    dc6.ColumnName = "Total";
                    dc6.Expression = "Cmimi * Sasia";//Multiplying the Price and Quantity DataColumns

                    dataTable.Columns.Add(dc);//Add them to the DataTable
                    dataTable.Columns.Add(dc2);
                    dataTable.Columns.Add(dc3);
                    dataTable.Columns.Add(dc4);
                    dataTable.Columns.Add(dc5);
                    dataTable.Columns.Add(dc6);

                    dtgartikujt.ItemsSource = dataTable.DefaultView;//Set the DataGrid ItemSource to this new generated DataTable
}

以及其余代码：

     long sum=0;
     private void enter(object sender, KeyEventArgs e)
            {
                try
                {
                    if (e.Key == Key.Enter)
                    {
                        SqlConnection com = new SqlConnection("Server = localhost; database = PrimaSOFT ; integrated security = true");

                        SqlCommand cmd = new SqlCommand("produktit", com);
                        cmd.CommandType = System.Data.CommandType.StoredProcedure;
                        cmd.Parameters.AddWithValue("@Barkodi", txtBarkodi.Text);
                        //Created a new DataTable

                        SqlDataAdapter da = new SqlDataAdapter(cmd);

                        com.Open();//Open the SQL connection

                        SqlDataReader reader = cmd.ExecuteReader();//Create a SqlDataReader

                        while (reader.Read())//For each row that the SQL query returns do
                        {
                            DataRow dr = dataTable.NewRow();//Create new DataRow to populate the DataTable (which is currently binded to the DataGrid)
                            dr[0] = reader[0];//Fill DataTable column 0 current row (Product) with reader[0] (Product from sql)
                            dr[1] = reader[1];
                            dr[2] = reader[2];
                            dr[3] = reader[3];
                            dr[4] = reader[4];
                            // sum+= Convert.ToInt64(reader[4]); // use the total index instead of 4 . or use reader["total"];

                            dataTable.Rows.Add(dr);//Add the new created DataRow to the DataTable
    // or maybe dtgartikujt.Rows.Add(dr);
                        }

// textbox1.Text=sum.Tostring();
                    }
                }