从combox中选择值后如何从Database绑定DataGridView [英] How to bind DataGridView from Database after selecting value from combox

问题描述

我在C＃中制作一个Windows窗体。我有一个DataGridView和一个组合框，我想要做的就是如果我在组合框中选择一个表，它应该在datagridview中显示结果。



我做过这样的事情：但是我得到这个错误：'System.Data.DataRowView'不包含定义

I am making a Windows Form in C#.I have a DataGridView and a combobox, all I want to do is if i select a table in the combobox, it should display me the results in the datagridview.

I have done something like this: BUT i' m getting this error : 'System.Data.DataRowView' does not contain a definition

private void cbTbl_SelectedIndexChanged(object sender, EventArgs e)
       {
           if (cbTbl.SelectedValue != null)
           {
               // Sql Server Connection and statement if a value is selected

               string CS = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;
               SqlConnection con = new SqlConnection(CS);
               SqlCommand sqlCmd = new SqlCommand();
               sqlCmd.Connection = con;
               sqlCmd.CommandType = CommandType.Text;
               sqlCmd.CommandText = ("SELECT * FROM " + cbTbl.SelectedValue); // Dynamically
               SqlDataAdapter sqlDataAdap = new SqlDataAdapter(sqlCmd);

               try
               {
                   con.Open();

                   dt = new DataTable();
                   sqlDataAdap.Fill(dt);
                   dataGridView1.AutoGenerateColumns = true;
                   dataGridView1.DataSource = dt;

               dataGridView1.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCells);

                   con.Close();

               }
               catch (Exception ex)
               {
                   MessageBox.Show(ex.Message);
               }
           }

我需要将SelectedItem强制转换为DataRowView才能获得来自这个DataRowView的价值但我不知道在哪里以及如何。



我用这种方法填充组合框：

I need to cast the SelectedItem into DataRowView in order to get a value from this DataRowView But i don't know where and how.

I'm filling the combobox with this method:

private void FillCombobox1()
{
// Sql Connection and statement
string C = (@"Data Source=");
SqlConnection con = new SqlConnection(C);


SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandText = ("SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES");
try
{

con.Open();

SqlDataAdapter adapter = new SqlDataAdapter(cmd);

DataTable dt = new DataTable();
adapter.Fill(dt);

//Fill combobox with data in DT
comboBox1.DataSource = dt;

//Display dbo Tables in cbAlt
comboBox1.DisplayMember = "TABLE_NAME";
comboBox1.ValueMember = "TABLE_NAME";

// Empty bzw. clear the combobox
comboBox1.SelectedIndex = -1;

}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
finally
{
con.Close();
}
}

推荐答案

嗯，这是一个常见的错误。填充组合框时，在绑定数据之前设置DisplayMember和ValueMember。像这样：

Well,that's a common error. When you fill the combobox, set the DisplayMember and ValueMember before binding the data. Like this:

//Display dbo Tables in cbAlt
comboBox1.DisplayMember = "TABLE_NAME";
comboBox1.ValueMember = "TABLE_NAME";
//Fill combobox with data in DT
comboBox1.DataSource = dt;

您遇到的问题是，当您使用comboBox1.DataSource = dt绑定数据时，会触发comboBox1.SelectedIndexChanged。但由于仍没有设置valueMember，传递给事件的是DataRowView，导致错误。



编辑



如果您想在将数据绑定到组合时阻止加载网格，请执行以下操作：

The problem you have is because when you bind the data with comboBox1.DataSource = dt, the comboBox1.SelectedIndexChanged is fired. But as the valueMember is still not set, what is passed to the event is a DataRowView,causing the error.

Edit

If you want to prevent to load the grid when you bind the data to the combo,do something like this:

bool firstLoad=true;
.
.
.

private void cbTbl_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (!firstLoad)
            {
              if (cbTbl.SelectedValue != null)  
              {  
                // Sql Server Connection and statement if a value is selected

                string CS = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;
                SqlConnection con = new SqlConnection(CS);
                SqlCommand sqlCmd = new SqlCommand();
                sqlCmd.Connection = con;
                sqlCmd.CommandType = CommandType.Text;
                sqlCmd.CommandText = ("SELECT * FROM " + cbTbl.SelectedValue); // Dynamically
                SqlDataAdapter sqlDataAdap = new SqlDataAdapter(sqlCmd);
 
                try 
                {
                    con.Open();
                   
                    dt = new DataTable();
                    sqlDataAdap.Fill(dt);
                    dataGridView1.AutoGenerateColumns = true;
                    dataGridView1.DataSource = dt;
                    
                dataGridView1.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCells);
                    
                    con.Close();
                   
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
             }
           }
           else
           {
             firstLoad=false;
           }
       }

也就是说，使用布尔变量来防止在组合框数据时加载数据网格视图绑定。

That is,use a boolean variable to prevent loading the datagrid view when the combobox data is binded.

这篇关于从combox中选择值后如何从Database绑定DataGridView的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！