Question

假设我有这段代码

Dim tab As String = "myTab"
Dim val As String = "field1"
Dim con As String = "...."
Dim qry As String 'should be: "Select * from " & tab & " where value = '" & val & "'"
Dim com As New OracleCommand (qry, con)...

还假设从数据库中检索查询字符串（即qry的值）。我无法将qry传递给oracle命令，因为它不会被评估，即变量没有绑定到它们的值，并且字符串会逐字传递给命令，从而导致错误。有没有办法评估字符串并将其作为VB语句执行？

Answer 1

使用参数非常简单，就像@muffi所说的那样。

脱离我的头顶：

    Dim tab As String = "myTab"
    Dim val As String = "field1"

    Using cmd As New OracleCommand("SELECT * FROM :table WHERE value = :value", con)
        cmd.Parameters.Add(New OracleParameter() {Direction = ParameterDirection.Input, ParameterName = "table", OracleDbType = OracleDbType.Varchar2, Value = tab})
        cmd.Parameters.Add(New OracleParameter() {Direction = ParameterDirection.Input, ParameterName = "value", OracleDbType = OracleDbType.Varchar2, Value = val})
        Using OracleDataReader reader As cmd.ExecuteReader()
            While reader.Read()
                Console.WriteLine(reader.GetString(0))
            End While
        End Using
    End Using

Visual Studio 2015.从字符串

1 个答案: