SqlCommand.ExecuteScalar Method
Definition
Important
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Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.
public:
override System::Object ^ ExecuteScalar();
public:
virtual System::Object ^ ExecuteScalar();
public override object ExecuteScalar ();
public object ExecuteScalar ();
override this.ExecuteScalar : unit -> obj
abstract member ExecuteScalar : unit -> obj
override this.ExecuteScalar : unit -> obj
Public Overrides Function ExecuteScalar () As Object
Public Function ExecuteScalar () As Object
Returns
The first column of the first row in the result set, or a null reference (Nothing
in Visual Basic) if the result set is empty. Returns a maximum of 2033 characters.
Implements
Exceptions
A SqlDbType other than Binary or VarBinary was used when Value was set to Stream. For more information about streaming, see SqlClient Streaming Support.
-or-
A SqlDbType other than Char, NChar, NVarChar, VarChar, or Xml was used when Value was set to TextReader.
-or-
A SqlDbType other than Xml was used when Value was set to XmlReader.
An exception occurred while executing the command against a locked row. This exception is not generated when you are using Microsoft .NET Framework version 1.0.
-or-
A timeout occurred during a streaming operation. For more information about streaming, see SqlClient Streaming Support.
The SqlConnection closed or dropped during a streaming operation. For more information about streaming, see SqlClient Streaming Support.
An error occurred in a Stream, XmlReader or TextReader object during a streaming operation. For more information about streaming, see SqlClient Streaming Support.
The Stream, XmlReader or TextReader object was closed during a streaming operation. For more information about streaming, see SqlClient Streaming Support.
Examples
The following example creates a SqlCommand and then executes it using ExecuteScalar. The example is passed a string representing a new value to be inserted into a table, and a string to use to connect to the data source. The function returns the new Identity column value if a new row was inserted, 0 on failure.
static public int AddProductCategory(string newName, string connString)
{
Int32 newProdID = 0;
string sql =
"INSERT INTO Production.ProductCategory (Name) VALUES (@Name); "
+ "SELECT CAST(scope_identity() AS int)";
using (SqlConnection conn = new SqlConnection(connString))
{
SqlCommand cmd = new SqlCommand(sql, conn);
cmd.Parameters.Add("@Name", SqlDbType.VarChar);
cmd.Parameters["@name"].Value = newName;
try
{
conn.Open();
newProdID = (Int32)cmd.ExecuteScalar();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
return (int)newProdID;
}
Public Function AddProductCategory( _
ByVal newName As String, ByVal connString As String) As Integer
Dim newProdID As Int32 = 0
Dim sql As String = _
"INSERT INTO Production.ProductCategory (Name) VALUES (@Name); " _
& "SELECT CAST(scope_identity() AS int);"
Using conn As New SqlConnection(connString)
Dim cmd As New SqlCommand(sql, conn)
cmd.Parameters.Add("@Name", SqlDbType.VarChar)
cmd.Parameters("@Name").Value = newName
Try
conn.Open()
newProdID = Convert.ToInt32(cmd.ExecuteScalar())
Catch ex As Exception
Console.WriteLine(ex.Message)
End Try
End Using
Return newProdID
End Function
Remarks
Use the ExecuteScalar method to retrieve a single value (for example, an aggregate value) from a database. This requires less code than using the ExecuteReader method, and then performing the operations that you need to generate the single value using the data returned by a SqlDataReader.
A typical ExecuteScalar query can be formatted as in the following C# example:
cmd.CommandText = "SELECT COUNT(*) FROM dbo.region";
Int32 count = (Int32) cmd.ExecuteScalar();
Applies to
See also
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