如何在 where 子句上基于 SqlCommand 或 SqlDataAdapter 填充 datagridview？ SqlDataAdapter 不适用于哪里？

Posted 2023-04-11

【中文标题】如何在 where 子句上基于 SqlCommand 或 SqlDataAdapter 填充 datagridview？ SqlDataAdapter 不适用于哪里？

【英文标题】：How to populate datagridview based on SqlCommand or SqlDataAdapter on where clause? SqlDataAdapter doesn't work with where?

【发布时间】：2021-05-20 21:48:58

【问题描述】：

// for delete it works, but for search no

// this is the delete part, afterwards I call the displaymethod to display the results after deletion
private void button1_Click(object sender, EventArgs e)

    if (txtArtistDelete.Text != "")
    
        command = new SqlCommand("delete from dbo.catalog where artist=@artist", connection);

        connection.Open();
        command.Parameters.AddWithValue("@artist", txtArtistDelete.Text);
        command.ExecuteNonQuery();
        connection.Close();

        MessageBox.Show("Record deleted successfully!");

        DisplayData();
        ClearData();
    
    else
    
        MessageBox.Show("Please select an artist to delete");
    


private void DisplayData()

    connection.Open();

    DataTable dt = new DataTable();
    adpter = new SqlDataAdapter("select * from dbo.catalog", connection);
    adpter.Fill(dt);

    dgvCatalog.DataSource = dt;
    connection.Close();


// but after search I can not do that
private void btnCautare_Click(object sender, EventArgs e)

    command = new SqlCommand("select * from dbo.catalog where title = @title", connection);

    connection.Open();
    command.Parameters.AddWithValue("@title", txtArtistDelete.Text);

    DataTable dt = new DataTable();
    adpter = new SqlDataAdapter("select * from dbo.catalog where title = @title", connection);
    adpter.Fill(dt);

    dgvCatalog.DataSource = dt;

    command.ExecuteNonQuery();
    connection.Close();


// I get this error: 
// System.Data.SqlClient.SqlException: 'Must declare the scalar variable "@title".'  
// I want to see in the datagridview only that searched record. 
// How can I do that with SqlCommand and SqlDataAdapter?     

如何使用 where 子句基于 SqlCommand 或 SqlDataAdapter 填充 datagridview？ SqlDataAdapter 不适用于 where

【问题讨论】：

dt.Fill(reader),?您可以从command.ExecuteReader() 获取读者。不要忘记使用 using 块处理所有 SQL 对象

注意：有很多 更有效的方法可以使用这些数据库提供程序对象，并且所有这些都有很好的文档记录。对于“搜索”，您可以使用 DGV 数据源的 RowFilter 属性过滤现有结果。

【参考方案1】：

您可以更高效地执行此操作，但让我们继续使用上面的代码。 正如错误所说“必须声明标量变量“@title”。”

用这个替换你的代码

command = new SqlCommand("select *  from dbo.catalog where title=@title", connection);
connection.Open();
command.Parameters.AddWithValue("@title", txtArtistDelete.Text);

DataTable dt = new DataTable();
adpter = new SqlDataAdapter(command); //Pass the SqlCommand object command as argument to SqlDataAdapter as it already contains the parameter @title in it
adpter.Fill(dt);
dgvCatalog.DataSource = dt;

command.ExecuteNonQuery();
connection.Close();