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_ .NET Framework Developer's Guide _
** 使用 ** ** Command ** ** 执行存储过程 **
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在数据驱动的应用程序中，存储过程可以提供很多优点。使用存储过程可以将数据库操作封装到一条简单的命令中，可以优化效能，可以增强安全性。只需要按照 SQL 语法在存储过程名后面跟带参数就可以调用该存储过程。使用 ADO.NET 中 ** Command ** 对象的 ** Parameters ** 属性你还可以明确的定义和使用 output 参数和 return 值。
调用存储过程时，要设置 ** Command ** 对象的 ** CommandType ** 属性为 ** StoreProcedure ** 。一旦设定了 ** CommandType ** 属性为 ** StoreProcedure ** ，你就可以使用 ** Parameters ** 集合来定义参数，就像下面的例子。
注意 使用 ** OdbcCommand ** 调用存储过程时要求提供完整的 ODBC CALL 语法。
SqlClient
[Visual Basic]
Dim nwindConn As SqlConnection = New SqlConnection("Data Source=localhost;Integrated Security=SSPI;" & _
"Initial Catalog=northwind")
Dim salesCMD As SqlCommand = New SqlCommand("SalesByCategory", nwindConn)
salesCMD.CommandType = CommandType.StoredProcedure
Dim myParm As SqlParameter = salesCMD.Parameters.Add("@CategoryName", SqlDbType.NVarChar, 15)
myParm.Value = "Beverages"
nwindConn.Open()
Dim myReader As SqlDataReader = salesCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1))
Do While myReader.Read()
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1))
Loop
myReader.Close()
nwindConn.Close()
[C#]
SqlConnection nwindConn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=northwind");
SqlCommand salesCMD = new SqlCommand("SalesByCategory", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
SqlParameter myParm = salesCMD.Parameters.Add("@CategoryName", SqlDbType.NVarChar, 15);
myParm.Value = "Beverages";
nwindConn.Open();
SqlDataReader myReader = salesCMD.ExecuteReader();
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1));
while (myReader.Read())
{
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1));
}
myReader.Close();
nwindConn.Close();
OleDb
[Visual Basic]
Dim nwindConn As OleDbConnection = New OleDbConnection("Provider=SQLOLEDB;Data Source=localhost;Integrated Security=SSPI;" & _
"Initial Catalog=northwind")
Dim salesCMD As OleDbCommand = New OleDbCommand("SalesByCategory", nwindConn)
salesCMD.CommandType = CommandType.StoredProcedure
Dim myParm As OleDbParameter = salesCMD.Parameters.Add("@CategoryName", OleDbType.VarChar, 15)
myParm.Value = "Beverages"
nwindConn.Open()
Dim myReader As OleDbDataReader = salesCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1))
Do While myReader.Read()
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1))
Loop
myReader.Close()
nwindConn.Close()
[C#]
OleDbConnection nwindConn = new OleDbConnection("Provider=SQLOLEDB;Data Source=localhost;Integrated Security=SSPI;" +
"Initial Catalog=northwind");
OleDbCommand salesCMD = new OleDbCommand("SalesByCategory", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
OleDbParameter myParm = salesCMD.Parameters.Add("@CategoryName", OleDbType.VarChar, 15);
myParm.Value = "Beverages";
nwindConn.Open();
OleDbDataReader myReader = salesCMD.ExecuteReader();
Console.WriteLine("\t{0}, {1}", myReader.GetName(0), myReader.GetName(1));
while (myReader.Read())
{
Console.WriteLine("\t{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1));
}
myReader.Close();
nwindConn.Close();
Odbc
[Visual Basic]
Dim nwindConn As OdbcConnection = New OdbcConnection("Driver={SQL Server};Server=localhost;Trusted_Connection=yes;" & _
"Database=northwind")
nwindConn.Open()
Dim salesCMD As OdbcCommand = New OdbcCommand("{ CALL SalesByCategory(?) }", nwindConn)
salesCMD.CommandType = CommandType.StoredProcedure
Dim myParm As OdbcParameter = salesCMD.Parameters.Add("@CategoryName", OdbcType.VarChar, 15)
myParm.Value = "Beverages"
Dim myReader As OdbcDataReader = salesCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", myReader.GetName(0), myReader.GetName(1))
Do While myReader.Read()
Console.WriteLine("{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1))
Loop
myReader.Close()
nwindConn.Close()
[C#]
OdbcConnection nwindConn = new OdbcConnection("Driver={SQL Server};Server=localhost;Trusted_Connection=yes;" +
"Database=northwind");
nwindConn.Open();
OdbcCommand salesCMD = new OdbcCommand("{ CALL SalesByCategory(?) }", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
OdbcParameter myParm = salesCMD.Parameters.Add("@CategoryName", OdbcType.VarChar, 15);
myParm.Value = "Beverages";
OdbcDataReader myReader = salesCMD.ExecuteReader();
Console.WriteLine("\t{0}, {1}", myReader.GetName(0), myReader.GetName(1));
while (myReader.Read())
{
Console.WriteLine("\t{0}, ${1}", myReader.GetString(0), myReader.GetDecimal(1));
}
myReader.Close();
nwindConn.Close();
一个 ** Parameter ** 对象可以使用 ** Parameter ** 构造器创建，也可以通过调用 ** Command ** 对象的 ** Parameters ** 集合的 ** Add ** 方法创建。 ** Parameters ** . Add 方法的输入参数可以和构造器相同，也可以使用一个存在的 ** Parameter ** 对象。用 ** System.DBNull.Value ** 设置 ** Parameter ** 的值为空。
如果要设置 ** Parameter ** 为非一般的输入参数时，必须设置 ** ParameterDirection ** 属性为 ** InputOutput ** ， ** Output ** ，或者 ** ReturnValue ** 。下面的例子演示了创建 ** Input ** , Output , 和 ** ReturnValue ** 参数的差别。
SqlClient
[Visual Basic]
Dim sampleCMD As SqlCommand = New SqlCommand("SampleProc", nwindConn)
sampleCMD.CommandType = CommandType.StoredProcedure
Dim sampParm As SqlParameter = sampleCMD.Parameters.Add("RETURN_VALUE", SqlDbType.Int)
sampParm.Direction = ParameterDirection.ReturnValue
sampParm = sampleCMD.Parameters.Add("@InputParm", SqlDbType.NVarChar, 12)
sampParm.Value = "Sample Value"
sampParm = sampleCMD.Parameters.Add("@OutputParm", SqlDbType.NVarChar, 28)
sampParm.Direction = ParameterDirection.Output
nwindConn.Open()
Dim sampReader As SqlDataReader = sampleCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1))
Do While sampReader.Read()
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1))
Loop
sampReader.Close()
nwindConn.Close()
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters("@OutputParm").Value)
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters("RETURN_VALUE").Value)
[C#]
SqlCommand sampleCMD = new SqlCommand("SampleProc", nwindConn);
sampleCMD.CommandType = CommandType.StoredProcedure;
SqlParameter sampParm = sampleCMD.Parameters.Add("RETURN_VALUE", SqlDbType.Int);
sampParm.Direction = ParameterDirection.ReturnValue;
sampParm = sampleCMD.Parameters.Add("@InputParm", SqlDbType.NVarChar, 12);
sampParm.Value = "Sample Value";
sampParm = sampleCMD.Parameters.Add("@OutputParm", SqlDbType.NVarChar, 28);
sampParm.Direction = ParameterDirection.Output;
nwindConn.Open();
SqlDataReader sampReader = sampleCMD.ExecuteReader();
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1));
while (sampReader.Read())
{
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1));
}
sampReader.Close();
nwindConn.Close();
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters["@OutputParm"].Value);
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters["RETURN_VALUE"].Value);
OleDb
[Visual Basic]
Dim sampleCMD As OleDbCommand = New OleDbCommand("SampleProc", nwindConn)
sampleCMD.CommandType = CommandType.StoredProcedure
Dim sampParm As OleDbParameter = sampleCMD.Parameters.Add("RETURN_VALUE", OleDbType.Integer)
sampParm.Direction = ParameterDirection.ReturnValue
sampParm = sampleCMD.Parameters.Add("@InputParm", OleDbType.VarChar, 12)
sampParm.Value = "Sample Value"
sampParm = sampleCMD.Parameters.Add("@OutputParm", OleDbType.VarChar, 28)
sampParm.Direction = ParameterDirection.Output
nwindConn.Open()
Dim sampReader As OleDbDataReader = sampleCMD.ExecuteReader()
Console.WriteLine("{0}, {1}", sampReader.GetName(0), sampReader.GetName(1))
Do While sampReader.Read()
Console.WriteLine("{0}, {1}", sampReader.GetInt32(0), sampReader.GetString(1))
Loop
sampReader.Close()
nwindConn.Close()
Console.WriteLine(" @OutputParm: {0}", sampleCMD.Parameters("@OutputParm").Value)
Console.WriteLine("RETURN_VALUE: {0}", sampleCMD.Parameters("RETURN_VALUE").Value)
[C#]
OleDbCommand sampleCMD = new OleDbCommand("SampleProc", nwindConn);
sampleCMD.CommandType = CommandType.StoredProcedure;
OleDbParameter sampParm = sampleCMD.Parameters.Add("RETURN_VALUE", OleDbType.Integer);
sampParm.Direction = ParameterDirection.ReturnValue;
sampParm = sampleCMD.Parameters.Add("@InputParm", OleDbType.VarChar, 12);
sampParm.Value = "Sample Value";
sampParm = sampleCMD.Parameters.Add("@OutputParm", OleDbType.VarChar, 28);
sampParm.Direction = ParameterDirection.Output;
nwindConn.Open();
OleDbDataReader sampReader = sampleCMD.ExecuteReader();
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