我收到此错误 必须声明标量变量"@"

Question

代码如下:

Private Sub Button5_Click(sender As Object, e As EventArgs)处理Button5。点击

con = New SqlConnection("Data Source=LAPTOP-16IIQENSSQLEXPRESS;Initial Catalog=students;Integrated Security=True")
con.Open()
cmd = New SqlCommand("select * from data where [Roll No.]=@[Roll No.]", con)
cmd.Parameters.Add("@Roll No.", SqlDbType.Int).Value = TextBox5.Text
Dim adp As New SqlDataAdapter(cmd)
Dim table As New DataTable()
adp.Fill(table)
If (table.Rows.Count() > 0) Then
DataGridView1.DataSource = table
TextBox2.Text = table.Rows(0)(0).ToString
TextBox1.Text = table.Rows(0)(1).ToString
TextBox3.Text = table.Rows(0)(2).ToString
TextBox4.Text = table.Rows(0)(3).ToString
Else
MessageBox.Show("No Data Found")
End If

End Sub

输入图片描述

Answer 1

您可以自由选择SQL参数的名称，它不需要匹配字段的名称。

因此，如果您调用参数@RollNo而不是@Roll No.(没有空格，没有点)，则不再需要在SQL中转义名称，这应该可以解决当前的问题。

改变:

cmd = New SqlCommand("select * from data where [Roll No.]=@[Roll No.]", con)
cmd.Parameters.Add("@Roll No.", SqlDbType.Int).Value = TextBox5.Text

:

cmd = New SqlCommand("select * from data where [Roll No.]=@RollNo", con)
cmd.Parameters.Add("@RollNo", SqlDbType.Int).Value = TextBox5.Text