wpf 如何使用 sqlclient 类使用 vb.net 计算 sql 表中的行数
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How to count number of rows in a sql table with vb.net using sqlclient class
提问by Sonia Rehman
SELECT count(*) FROM table name
this above code work fine in standalone sql table, but who can I do this simple task with in vb.net wpf project ?
上面的代码在独立的 sql 表中工作正常，但是我可以在 vb.net wpf 项目中与谁一起完成这个简单的任务？
采纳答案by Sachu
This is only a sample ..just check and try your own way.
这只是一个示例..只需检查并尝试自己的方式。
Sample:
样本：
Dim connetionString As String
Dim connection As SqlConnection
Dim command As SqlCommand
Dim sql As String
connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;
User ID=UserName;Password=Password"
sql = "Select count(*) from table"
connection = New SqlConnection(connetionString)
Try
connection.Open()
command = New SqlCommand(sql, connection)
Dim sqlReader As SqlDataReader = command.ExecuteReader()
While sqlReader.Read()
MsgBox("Count =" & sqlReader.Item(0))
End While
sqlReader.Close()
command.Dispose()
connection.Close()
Catch ex As Exception
MsgBox("Can not open connection ! ")
End Try
If your query return more than one values you can use SqlDataReader(), but if you are sure your query will return only a single value you can use ExecuteScalar()and if your query wont return any result, eg:- insert.it will insert value not return any data so we can use ExecuteNonQuery().The ExecuteNonQuery() will return a result which indicate is it successful or failure. If you want you can assign the same else no need.
如果您的查询返回多个值，您可以使用SqlDataReader()，但如果您确定您的查询将只返回一个您可以使用的值，ExecuteScalar()并且如果您的查询不会返回任何结果，例如：- insert.it 将插入值而不返回任何数据所以我们可以使用ExecuteNonQuery(). ExecuteNonQuery() 将返回一个结果，表明它是成功还是失败。如果你愿意，你可以分配相同的 else 没有必要。
回答by har07
Use SqlCommand.ExecuteScalar()method to execute query that return singular/scalar value (example based on that link) :
使用SqlCommand.ExecuteScalar()方法执行返回单数/标量值的查询（基于该链接的示例）：
Dim count As Integer
Dim connString = "connection string to your database here"
Using conn As New SqlConnection(connString)
Dim cmd As New SqlCommand("SELECT COUNT(*) FROM MyTable", conn)
Try
conn.Open()
count = Convert.ToInt32(cmd.ExecuteScalar())
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Using
