我无法计算数据库表中的行数。 [英] I am unable to count rows from my database table.

问题描述

private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                con.Open();
                cmd.CommandText = "select count(*) from test;";
                cmd.Connection = con;
                int a = (int)cmd.ExecuteScalar();
                dr.Close();
                con.Close();
                string status = Convert.ToString(a);
                label1.Text = status;
            }
            catch (Exception err)
            {
                MessageBox.Show(err.Message);
                this.Close();
            }
        }

推荐答案

我想你错过了连接细节

I think you miss the connection details

string connectionString = "Connection String details";
SqlConnection con = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand();

更好地了解这个

Better you follw this

//Connecion string .....
            SqlCommand cmd= new SqlCommand("select count(*) from test", con);
	    int noRows;
            con.Open();
	    noRows = cmd.ExecuteNonQuery();
	    con.Close();
	    label1.Text= Convert.ToString(noRows);

您没有发起连接或命令对象。



谢谢......

Hi,

You did not initiate your connection or command object.

Thanks...

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