C# Signature:

/// <summary>
/// SQLDataSources returns information about a data source. This function is implemented solely by the Driver Manager.
/// </summary>
/// <param name="EnvironmentHandle">[Input] Environment handle.</param>
/// <param name="Direction">[Input] Determines which data source the Driver Manager returns information on.</param>
/// <param name="ServerName">[Output] Pointer to a buffer in which to return the data source name.</param>
/// <param name="BufferLength1">[Input] Length of the *ServerName buffer, in characters; this does not need to be longer than SQL_MAX_DSN_LENGTH plus the null-termination character.</param>
/// <param name="NameLength1Ptr">[Output] Pointer to a buffer in which to return the total number of bytes (excluding the null-termination byte)
/// available to return in *ServerName. If the number of bytes available to return is greater than or equal to BufferLength1, the data
/// source name in *ServerName is truncated to BufferLength1 minus the length of a null-termination character. </param>
/// <param name="Description">[Output] Pointer to a buffer in which to return the description of the driver associated with the data source.
/// For example, dBASE or SQL Server.</param>
/// <param name="BufferLength2">[Input] Length in characters of the *Description buffer.</param>
/// <param name="NameLength2Ptr">[Output] Pointer to a buffer in which to return the total number of bytes (excluding the null-termination
/// byte) available to return in *Description. If the number of bytes available to return is greater than or equal to BufferLength2,
/// the driver description in *Description is truncated to BufferLength2 minus the length of a null-termination character.</param>
/// <returns>SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_NO_DATA, SQL_ERROR, or SQL_INVALID_HANDLE.</returns>
[DllImport("odbc32.dll", CharSet=CharSet.Ansi))]
static extern short SQLDataSources(IntPtr EnvironmentHandle, short Direction,
    StringBuilder ServerName, short BufferLength1, ref short NameLength1Ptr,
    StringBuilder Description, short BufferLength2, ref short NameLength2Ptr);

VB Signature:

Declare Function SQLDataSources Lib "odbc32.dll" (ByVal EnvironmentHandle As Integer, ByVal Direction As Short, _
    ByVal ServerName As String, ByVal BufferLength1 As Short, ByRef NameLength1Ptr As Short, _
    ByVal Description As String, ByVal BufferLength2 As Short, ByRef NameLength2Ptr As Short) As Short

User-Defined Types:

None.

Notes:

MSDN Documentation was sourced for the precise parameter definitions and return values.

You must provide an Environment Handle provided by SQLAllocHandle as the first parameter. SQLAllocHandle is a replacement for SQLAllocEnv. When using SQLAllocHandle, you must call SQLSetEnvAttr and set the SQL_ATTR_ODBC_VERSION attribute to SQL_OV_ODBC3 before calling SQLDataSources.

Tips & Tricks:

Depending on the value of Direction, you may access System DSN, User DSN or both. Since the same DSN name may be used in User and System DSN, watch out for possible duplicate values.

Sample Code:

One use of this function is to populate a combobox with available DSN's in a login screen...

Here is a simple function to obtain the Data Source Names installed on the system (this functionality is not available in ODBC.net):

public const ushort SQL_HANDLE_ENV = 1;
public const short SQL_SUCCESS = 0;
public const short SQL_SUCCESS_WITH_INFO = 1;
public const short SQL_NO_DATA = 100;
public const int SQL_ATTR_ODBC_VERSION = 200;
public const int SQL_OV_ODBC3 = 3;
public const short SQL_FETCH_NEXT = 1;
public const short SQL_FETCH_FIRST = 2;
public const int MAX_DSN_LENGTH = 32;

/// <summary>
/// Obtains all the ODBC DSNs installed on the system and returns them in a List<string> object.
/// </summary>
public static List<string> GetOdbcDataSources()
{
    int sql_env_handle = 0;
    short rc = 0;
    StringBuilder dsn_name = new StringBuilder(MAX_DSN_LENGTH);
    StringBuilder desc_name = new StringBuilder(128);
    short dsn_name_len = 0,desc_len = 0;
    List<String> rv = new List<String>();

    try
    {
    rc = SQLAllocHandle(SQL_HANDLE_ENV, 0, out sql_env_handle);
    if ((rc != SQL_SUCCESS) && (rc != SQL_SUCCESS_WITH_INFO))
        throw new Exception("Could not allocate ODBC Environment handle");
    rc = SQLSetEnvAttr(sql_env_handle, SQL_ATTR_ODBC_VERSION, (IntPtr)SQL_OV_ODBC3, 0);
    if ((rc != SQL_SUCCESS) && (rc != SQL_SUCCESS_WITH_INFO))
        throw new Exception("Could not setup ODBC Environment handle");
    rc = SQLDataSources(sql_env_handle, SQL_FETCH_FIRST, dsn_name, (short)dsn_name.Capacity, ref dsn_name_len, desc_name, (short) desc_name.Capacity, ref desc_len);
    if ((rc != SQL_SUCCESS) && (rc != SQL_SUCCESS_WITH_INFO) && (rc != SQL_NO_DATA))
        throw new Exception("Error getting ODBC Data Sources");
    while ((rc == SQL_SUCCESS) || (rc == SQL_SUCCESS_WITH_INFO))
    {
        rv.Add(dsn_name.ToString());
        rc = SQLDataSources(sql_env_handle, SQL_FETCH_NEXT, dsn_name, (short)dsn_name.Capacity, ref dsn_name_len, desc_name, (short)desc_name.Capacity, ref desc_len);
        if ((rc != SQL_SUCCESS) && (rc != SQL_SUCCESS_WITH_INFO) && (rc != SQL_NO_DATA))
        throw new Exception("Error getting ODBC Data Sources");
    }
    }
    finally
    {
    if (sql_env_handle != 0)
    {
        rc = SQLFreeHandle(SQL_HANDLE_ENV, sql_env_handle);
        if ((rc != SQL_SUCCESS) && (rc != SQL_SUCCESS_WITH_INFO))
        throw new Exception("Could not free ODBC Environment handle");
    }
    }
    return rv;
}

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