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OleDbCommand.ExecuteScalar Method

.NET Framework 4.5

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.

Namespace: System.Data.OleDb
Assembly: System.Data (in System.Data.dll)

Syntax

C++

public override Object ExecuteScalar()

Return Value

Type: System.Object
The first column of the first row in the result set, or a null reference if the result set is empty.

Implements

IDbCommand.ExecuteScalar()

Exceptions

Exception	Condition
InvalidOperationException	Cannot execute a command within a transaction context that differs from the context in which the connection was originally enlisted.

Remarks

Use the ExecuteScalar method to retrieve a single value, for example, an aggregate value, from a data source. This requires less code than using the ExecuteReader method, and then performing the operations that are required to generate the single value using the data returned by an OleDbDataReader.

A typical ExecuteScalar query can be formatted as in the following C# example:

CommandText = "SELECT COUNT(*) FROM region";
Int32 count = (int32) ExecuteScalar();

Examples

The following example creates an OleDbCommand and then executes it using ExecuteScalar. The example is passed a string that is an SQL statement that returns an aggregate result, and a string to use to connect to the data source.

public void CreateMyOleDbCommand(string queryString, 
    OleDbConnection connection) 
{
    OleDbCommand command = new OleDbCommand(queryString, connection);
    command.Connection.Open();
    command.ExecuteScalar();
    connection.Close();
}

Version Information

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Platforms

Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference

OleDbCommand Class

System.Data.OleDb Namespace

Other Resources

Commands and Parameters (ADO.NET)

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