使用Command执行存储过程

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();

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);

Odbc

[Visual Basic]

Dim sampleCMD As OdbcCommand = New OdbcCommand("{ ? = CALL SampleProc(?, ?) }", nwindConn)

sampleCMD.CommandType = CommandType.StoredProcedure

Dim sampParm As OdbcParameter = sampleCMD.Parameters.Add("RETURN_VALUE", OdbcType.Int)

sampParm.Direction = ParameterDirection.ReturnValue

sampParm = sampleCMD.Parameters.Add("@InputParm", OdbcType.VarChar, 12)

sampParm.Value = "Sample Value"

sampParm = sampleCMD.Parameters.Add("@OutputParm", OdbcType.VarChar, 28)

sampParm.Direction = ParameterDirection.Output

nwindConn.Open()

Dim sampReader As OdbcDataReader = 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#]

OdbcCommand sampleCMD = new OdbcCommand("{ ? = CALL SampleProc(?, ?) }", nwindConn);

sampleCMD.CommandType = CommandType.StoredProcedure;

OdbcParameter sampParm = sampleCMD.Parameters.Add("RETURN_VALUE", OdbcType.Int);

sampParm.Direction = ParameterDirection.ReturnValue;

sampParm = sampleCMD.Parameters.Add("@InputParm", OdbcType.VarChar, 12);

sampParm.Value = "Sample Value";

sampParm = sampleCMD.Parameters.Add("@OutputParm", OdbcType.VarChar, 28);

sampParm.Direction = ParameterDirection.Output;

nwindConn.Open();

OdbcDataReader 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);

在SqlCommand中使用参数

在SqlCommand中使用参数时，参数的名字必须和存储过程中相应参数的名字匹配。SQL SERVER的.NET Framework Data Provider将存储过程中的参数视为命名参数并且搜索与之匹配的参数标记。

SQL SERVER的.NET Framework Data Provider不支持使用问号标记（?）作为占位符来向SQL语句或者存储过程传递参数。既然如此，你必须命名参数，就下面一样：

SELECT * FROM Customers WHERE CustomerID = @CustomerID

在OleDbCommand 和OdbcCommand中使用参数

在OleDbCommand或者OdbcCommand中使用参数时，参数添加到Parameters集合中的顺序必须和存储过程中参数定义的顺序匹配。OLE DB和ODBC的.NET Framework数据供应程序将存储过程的参数视为占位符，按照顺序来给参数赋值。另外，返回参数必须是第一个被加入到Parameters集合中的参数。

OLE DB和ODBC的.NET Framework数据供应程序不提供使用命名参数来向SQL语句或存储过程传递参数。为此，你必须使用问号(?)占位符，就像下面一样：

SELECT * FROM Customers WHERE CustomerID = ?

因此，向 Parameters 集合添加 Parameter 对象的顺序必须直接对应于该参数的问号占位符的位置。

导出参数信息

参数也可以使用 CommandBuilder 类从存储过程导出。SqlCommandBuilder 和 OleDbCommandBuilder 类都提供了静态方法 DeriveParameters，该静态方法将自动使用存储过程中的参数信息填充 Command 对象的 Parameters 集合。请注意，DeriveParameters 将改写 Command 的任何现有参数信息。

导出参数信息时需要经历一个到数据源的附加行程，以获取参数信息。如果参数信息在设计时是已知的，则可以通过显式设置参数来提高应用程序的性能。

以下代码示例显示如何使用 CommandBuilder.DeriveParameters 来填充 Command 对象的 Parameters 集合。

[Visual Basic]

Dim nwindConn As SqlConnection = New SqlConnection("Data Source=localhost;Initial Catalog=Northwind;Integrated Security=SSPI;")

Dim salesCMD As SqlCommand = New SqlCommand("Sales By Year", nwindConn)

salesCMD.CommandType = CommandType.StoredProcedure

nwindConn.Open()

SqlCommandBuilder.DeriveParameters(salesCMD)

nwindConn.Close()

[C#]

SqlConnection nwindConn = new SqlConnection("Data Source=localhost;Initial Catalog=Northwind;Integrated Security=SSPI;");

SqlCommand salesCMD = new SqlCommand("Sales By Year", nwindConn);

salesCMD.CommandType = CommandType.StoredProcedure;

nwindConn.Open();

SqlCommandBuilder.DeriveParameters(salesCMD);

nwindConn.Close();