Question

我一直在尝试创建一些与DB无关的代码，如下所示：

IDbCommand command = connection.CreateCommand();
command.CommandText = "...";

IDbDataParameter param1 = command.CreateParameter();
param1.ParameterName = "param1";
param1.Value = "value";
command.Parameters.Add(param1);

适用于mysql的命令文本是：

select * from mytable where field1 = ?param1

适用于sqlserver的命令文本是：

select * from mytable where field1 = @param1

是否有某种形式适用于两者？

编辑：

SQL Server 2008R2
MySQL 5.0.X

Answer 1

不，我认为没有这样的方法。所以你必须提供自己的：

public static String GetProviderParameter(string paramName, IDbConnection con)
{
    string prefix = "";
    if(con is System.Data.SqlClient.SqlConnection)
        prefix = "@";
    else if(con is System.Data.OleDb.OleDbConnection)
        prefix =  "?";
    else if(con is System.Data.Odbc.OdbcConnection)
        prefix =  "?";
    else if(con is MySql.Data.MySqlClient.MySqlConnection)
        prefix =  "?";

    return prefix + paramName;
}

用法：

param1.ParameterName = GetProviderParameter("param1", connection);

或者您可以使用this扩展程序使用反射来使用protected类中的GetParameterName方法DbCommandBuilder：

public static class Db
{
    static readonly Func<DbConnection, DbProviderFactory> getDbProviderFactory = 
        (Func<DbConnection, DbProviderFactory>)Delegate.CreateDelegate(typeof(Func<DbConnection, DbProviderFactory>), typeof(DbConnection).GetProperty("DbProviderFactory", BindingFlags.Instance | BindingFlags.NonPublic).GetGetMethod(true));
    static readonly Func<DbCommandBuilder, string, string> getParameterName =
        (Func<DbCommandBuilder, string, string>)Delegate.CreateDelegate(typeof(Func<DbCommandBuilder, string, string>), typeof(DbCommandBuilder).GetMethod("GetParameterName", BindingFlags.Instance | BindingFlags.NonPublic, Type.DefaultBinder, new Type[] { typeof(string) }, null));

    public static DbProviderFactory GetProviderFactory(this DbConnection connection)
    {
        return getDbProviderFactory(connection);
    }

    public static string GetParameterName(this DbConnection connection, string paramName)
    {
        DbCommandBuilder builder = GetProviderFactory(connection).CreateCommandBuilder();

        return getParameterName(builder, paramName);
    }
}

然后很简单：

param1.ParameterName = connection.GetParameterName("param1");

Answer 2

您可以将它们用于：

select * from mytable where field1 = @param1

请参阅MySql here的文档。

IDbCommand为MySQL和SQL Server命名参数

2 个答案: